Oracle10g - Data Guard Administration - D40345

D17316GC11Edition 1.1January 2005D40345

Oracle Database 10g: Data Guard Administration

Student Guide

Copyright © 2005, Oracle. All rights reserved.

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Authors

Donna KeeslingRic Van Dyke

Technical Contributorsand Reviewers

Christopher AndrewsLarry BaumannTammy Bednar Harald van BreederodeMary Bryksa Bernhard de Cock Buning Larry Carpenter Sean Connolly Raymond Dutcher Mark Fuller Joel GoodmanRaymond GuzmanZiemowit JankowskiNitin Karkhanis Jiangbin LuoAshish Ray Vivian Schupmann Jim SpillerS Matt Taylor Michael Verheij John Watson

Publisher

Nita Brozowski

Preface

1 Oracle Data Guard: OverviewObjectives 1-2Causes of Data Loss 1-3Every System Faces Down Time 1-4What Is Oracle Data Guard? 1-5Types of Standby Databases 1-6Oracle Data Guard Broker Framework 1-7Types of Services 1-8Role Transitions: Switchover and Failover 1-9Data-Protection Modes 1-11Benefits of Implementing Oracle Data Guard 1-13Role of Data Guard in a High Availability Architecture 1-14Oracle Data Guard and Real Application Clusters 1-16Maximum Availability Architecture 1-17Summary 1-18Practice 1: Overview 1-19

2 Understanding the Oracle Data Guard ArchitectureObjectives 2-2Data Guard Operational Requirements: Hardware and Operating System 2-3Data Guard Operational Requirements: Oracle Database Software 2-4Oracle Data Guard: Architecture 2-6Primary Database Flow 2-7Standby Database Flow 2-8Standby Redo Logs 2-9Data Guard Redo Apply: Architecture 2-10Data Guard SQL Apply: Architecture 2-12SQL Apply Process: Architecture 2-13Real-Time Apply 2-14Setting the DB_UNIQUE_NAME Parameter 2-16Specifying Role-Based Destinations 2-17Combinations for VALID_FOR 2-19Identifying Destination Settings 2-20Standby Redo Log Configuration 2-21Number of Standby Redo Logs 2-22Using SQL to Add Standby Redo Logs 2-23Using Enterprise Manager to Add Standby Redo Logs 2-24Standby Database Modes 2-25Summary 2-27Practice 2-1: Overview (Architecture) 2-28Practice 2-2: Overview (Installing the Oracle Management Agent) 2-29Practice 2-3: Overview (Configuring Your Primary Database) 2-30

Contents

iii

3 Data Guard Broker and Enterprise ManagerObjectives 3-2Features of Data Guard Broker 3-3Data Guard Broker: Components 3-4Data Guard Broker: Configurations 3-5Data Guard Broker: Management Model 3-6Data Guard Broker: Architecture 3-7Life Cycle of a Broker Configuration 3-8Data Guard Broker: Requirements 3-9Data Guard Broker and the SPFILE 3-11Data Guard Monitor: DMON Process 3-13Data Guard Monitor: Configuration File 3-14Benefits of Using the Data Guard Broker 3-15Data Guard Broker Interfaces 3-17Using Oracle Enterprise Manager 10g Grid Control 3-19Data Guard Overview Page 3-20Enterprise Manager Metrics and Alerts 3-21Using Data Guard Metrics 3-22Managing Data Guard Metrics 3-23Benefits of Using Enterprise Manager 3-24Using the Command-Line Interface of the Data Guard Broker 3-25Summary 3-27

4 Creating a Configuration with Enterprise ManagerObjectives 4-2Enabling FORCE LOGGING Mode 4-3Using Enterprise Manager to Create a Broker Configuration 4-5Creating a Configuration 4-6Using the Add Standby Database Wizard 4-8Step 1: Specify the Backup Type 4-9Step 2: Specify the Backup Options 4-10Step 3: Select the Oracle Home – Instance Name 4-11Step 3: Select the Oracle Home – Oracle Home 4-12Step 4: Specify the Standby Database File Locations – Access Method 4-13Step 4: Specify the Standby Database File Locations – File Locations 4-14Step 5: Specify Standby Database Configuration Parameters 4-15Step 6: Review the Configuration Information 4-16Standby Database Creation: Processing 4-17Standby Database Creation: Progress 4-19Standby Database Creation: Job Details 4-20Verifying a Configuration 4-21Reviewing Results of the Verify Operation 4-22Creating Standby Redo Logs 4-23Viewing the Data Guard Configuration Status 4-24Viewing Data Guard Performance 4-25Summary 4-27Practice 4: Overview 4-28

iv

5 Creating a Physical Standby Database by Using SQLObjectives 5-2Steps to Create a Physical Standby Database 5-3Preparing the Primary Database 5-4Initialization Parameters on the Primary Database 5-5LOG_ARCHIVE_CONFIG 5-6LOG_ARCHIVE_DEST_n 5-7LOCATION and SERVICE Attributes 5-8LOG_ARCHIVE_DEST_STATE_n 5-9Specifying Values for DB_FILE_NAME_CONVERT 5-10Specifying Values for LOG_FILE_NAME_CONVERT 5-11Specifying a Value for LOG_ARCHIVE_FORMAT 5-12Specifying a Value for STANDBY_FILE_MANAGEMENT 5-13ARCHIVE_LAG_TARGET 5-14LOG_ARCHIVE_TRACE Parameter 5-15LOG_ARCHIVE_TRACE 5-16Backing Up the Primary Database by Using RMAN 5-17Creating a Control File for the Standby Database 5-18Copying Files to the Standby Database System 5-19Oracle Managed Files (OMF) and Automatic Storage Management (ASM) 5-20Initialization Parameters on the Standby 5-21Specifying a Value for STANDBY_ARCHIVE_DEST 5-22Setting Up the Environment to Support the Standby Database 5-23Starting Up the Physical Standby Database 5-25Additional Configuration Tasks 5-26Special Note: Standby Database on Same System 5-27Summary 5-28

6 Data Protection Modes and Log Transport ServicesObjectives 6-2Data Protection Modes and Log Transport Modes 6-3Attributes of LOG_ARCHIVE_DEST_n 6-4Setting the Log Transport Mode 6-6Data Protection Modes 6-8Maximum Protection 6-9Maximum Availability 6-10Maximum Performance 6-11Setting the Data Protection Mode 6-12Setting the Data Protection Mode by Using the CLI 6-14Setting the Protection Mode by Using SQL 6-15Delaying the Application of Redo 6-16Using Enterprise Manager to Delay the Application of Redo 6-17Setting LOG_ARCHIVE_DEST_n to Delay the Application of Redo 6-18Using Flashback Database Instead of Apply Delay 6-19Additional Attributes That Affect Log Transport Services 6-20ALTERNATE and NOALTERNATE Attributes 6-21MAX_FAILURE and NOMAX_FAILURE Attributes 6-22NET_TIMEOUT and NONET_TIMEOUT Attributes 6-23REOPEN and NOREOPEN Attributes 6-24Summary 6-25Practice 6: Overview 6-26

v

7 Data Guard SQL Apply ArchitectureObjectives 7-2Benefits of Implementing a Logical Standby Database 7-3Securing Your Logical Standby Database 7-5Preparing to Create a Logical Standby Database 7-6Unsupported Data Types 7-7Unsupported Objects 7-8Checking for Tables with Unsupported Data Types 7-9Unsupported DDL Commands 7-10Ensuring Unique Row Identifiers 7-11Adding a Disabled Primary Key RELY Constraint 7-13Supplemental Logging 7-14Enabling Supplemental Logging 7-16Verifying Values of Initialization Parameters 7-17Creating a Logical Standby Database with Enterprise Manager 7-18Using the Add Standby Database Wizard 7-19Step 1: Specifying the Backup Type 7-20Step 2: Specifying the Backup Options 7-21Step 3: Selecting the Oracle Home – Instance Name 7-22Step 4: Specifying the Standby Database File Locations – Access Method 7-23Step 4: Specifying the Standby Database File Location – File Locations 7-24Step 5: Specifying Standby Database Configuration Parameters 7-25Step 6: Reviewing the Configuration Information 7-26Standby Database Creation Processing 7-27Resolving a Failed or Canceled Configuration Creation 7-28Summary 7-29Practice 7: Overview 7-30

8 Creating a Logical Standby Database by Using SQLObjectives 8-2Preparing to Create a Logical Standby Database 8-3Creating a Logical Standby Database 8-4Step 1: Create a Physical Standby Database 8-5Step 2: Prepare the Primary Database to Support a Logical Standby Database 8-6Step 3: Prepare to Transition to a Logical Standby Database 8-8Step 4: Start the Logical Standby Database 8-10Step 5: Verify That the Logical Standby Database Is Performing Properly 8-12Additional Configuration Tasks 8-14Summary 8-15

9 Switchover and FailoverObjectives 9-2Types of Roles in an Oracle Data Guard Configuration 9-3Role Management Services 9-4Role Transitions: Switchover and Failover 9-5Role Transition Decision Tree 9-7Switchover 9-8Switchover: Before 9-9Switchover: After 9-10

vi

Standby Redo Logs and Switchovers 9-11Preparing for a Switchover 9-12Performing a Switchover with Enterprise Manager 9-13Performing a Switchover to a Physical Standby by Using SQL 9-16Performing a Switchover to a Logical Standby by Using SQL 9-18Considerations When Performing a Switchover to a Logical Standby Database 9-23Situations That Prevent a Switchover 9-25Failover 9-26Failover Considerations 9-27Performing a Failover with Enterprise Manager 9-28Performing a Failover to a Physical Standby Database 9-31Performing a Failover to a Logical Standby Database 9-32Performing a Failover to a Physical Standby Database by Using SQL 9-33Performing a Failover to a Logical Standby Database by Using SQL 9-36Activating a Standby Database 9-38Using Flashback Database After Failover 9-39Summary 9-42Practice 9: Overview 9-43

10 Using Data Guard with RACObjectives 10-2Real Application Clusters and Data Guard 10-3Configuration Considerations with RAC 10-4Multi-Instance Primary with a Single-Instance Standby 10-6Multi-Instance Primary with a Multi-Instance Standby 10-7Log Transport with RAC to RAC 10-8Setting Up a Primary Database with RAC 10-9Setting Up a Standby Database with RAC 10-10Assigning Threads to Standby Redo Log Groups 10-11Apply Instance Failover 10-12Role Transitions with RAC 10-14Troubleshooting 10-15Summary 10-17

11 Other Considerations for Oracle Data GuardObjectives 11-2Offloading Backups to a Physical Standby 11-3Backing Up a Physical Standby Database with RMAN 11-4Backup and Recovery of a Logical Standby Database 11-6Using Flashback Database and Real-Time Apply 11-7Using Flashback Database After RESETLOGS 11-8Enabling Redo Encryption 11-10Cascaded Redo Log Destinations 11-11Configuring Cascaded Redo Log Destinations: Physical Standby 11-12Configuring Cascaded Redo Log Destinations: Logical Standby 11-14Role Transitions with Cascaded Redo Log Destinations 11-16Summary 11-17

vii

12 WorkshopObjectives 12-2Workshop Premise 12-3Workshop Flow 12-4Workshop Scenarios 12-5Summary 12-8Workshop Steps 12-10

Appendix A: Practices and Solutions

Appendix B: Oracle Data Guard: History

viii

Preface

Preface - 3

Profile

Before You Begin This CourseBefore you begin this course, you should have the following qualifications:• Thorough knowledge of Oracle Database 10g• Working experience with Oracle Database 10g and Oracle Enterprise Manager Grid Control

Prerequisites • Oracle Database 10g: Administration Workshop I (D17090GC10)• Oracle Database 10g: Administration Workshop II (D17092GC20)• Suggested: Oracle Enterprise Manager 10g Grid Control (D17244GC10)

How This Course Is OrganizedOracle Database 10g: Data Guard Administration is an instructor-led course featuring lectures and hands-on exercises. Online demonstrations and written practice sessions reinforce the concepts and skills introduced.

Preface - 4

Related Publications

Oracle PublicationsTitle Part NumberOracle Database Administrator's Guide 10g Release 1 (10.1) B10739-01Oracle Database Concepts 10g Release 1 (10.1) B10743-01Oracle Database Performance Tuning Guide10g Release 1 (10.1) B10752-01Oracle Database Reference 10g Release 1 (10.1) B10755-01Oracle Database SQL Reference 10g Release 1 (10.1) B10759-01Oracle Database Utilities 10g Release 1 (10.1) B10825-01Oracle Data Guard Broker 10g Release 1 (10.1) B10822-01Oracle Data Guard Concepts and Administration 10g Release 1 (10.1) B10823-01

Additional Publications• System release bulletins• Installation and user’s guides• International Oracle User’s Group (IOUG) articles• Oracle Magazine


Oracle Data Guard: Overview

Oracle Database 10g: Data Guard Administration 1-2


Objectives

After completing this lesson, you should be able to do the following:• Describe the factors that affect planned and

unplanned down time• Describe the basic components of Oracle Data

Guard• Explain the differences between physical and

logical standby databases• Explain the benefits of creating a Data Guard

environment• Explain the use of Data Guard in high availability

architectures



Causes of Data Loss

Source: Disaster Recovery Journal

Natural disasters 3%

Software corruption 4%

Computer viruses 7%

Human errors 36%

Hardware & system errors 49%

Causes of Data LossAccording to a survey published in the Disaster Recovery Journal (DRJ), the leading causes of data loss were not natural disasters but hardware failures and human errors.The goal of Oracle Data Guard is to provide an effective safeguard against data loss. Data Guard provides enterprises with complete data protection, data recovery, and data availability, ensuring around-the-clock business continuity.



Every System Faces Down Time

Planneddown time

Unplanneddown time

Systemchanges

Datachanges

Datafailures

Computerfailures

Corruption

Human error

Sitefailure

Storagefailure

Unplanned Versus Planned Down TimeEvery system faces both unplanned and planned down time. It is important to consider causes of both unplanned and planned down time when designing a fault-tolerant, resilient infrastructure.Unplanned down time consists of the following:

• Computer failures: Down time occurs when there is a power outage or a system crash.

• Data failures: Data failure is the loss, damage, or corruption of critical enterprise data. Causes of data failure include:

- Storage failure: Disk crash or space limitations- Human error: Down time occurs when someone inadvertently drops a table or

the system administrator makes an error.- Corruption: Caused by a faulty component in the I/O stack- Site failure: Down time occurs when there is some sort of data corruption or

natural disaster such as a flood, fire, or earthquake. Planned down time includes routine operations, periodic maintenance, and new deployments. Planned down time includes the following:

• Data changes: Table redefinition and index rebuild• System changes: Down time occurs during hardware and operating-system

upgrades.



What Is Oracle Data Guard?

Productiondatabase

Standbydatabase

Database Database copy

Redo transport

Ora

cle

Net

What Is Oracle Data Guard?Oracle Data Guard is a management, monitoring, and automation software infrastructure that works with a production database and one or more standby databases to protect your data against failures, errors, and corruptions that might otherwise destroy your database. It protects critical data by providing facilities to automate the creation, management, and monitoring of the databases and other components in a Data Guard configuration. It automates the process of maintaining a copy of an Oracle production database (called a standby database) that can be used if the production database is taken offline for routine maintenance or becomes damaged.In a Data Guard configuration, a production database is referred to as a primary database. A standby database is a transactionally consistent copy of the primary database. Using a backup copy of the primary database, you can create from one to nine standby databases. The standby databases, together with the primary database, make up a Data Guard configuration. Each standby database is associated with only one primary database.Note: You can use the Cascaded Redo Log Destinations feature to incorporate more than nine standby databases in your configuration. Refer to the “Other Considerations forOracle Data Guard” lesson for additional information on this feature.



Types of Standby Databases

There are two types of standby databases:• Physical standby database

– Identical to the primary database on a block-for-block basis

– Synchronized with the primary database through application of redo data received from the primary database

• Logical standby database– Shares the same schema definition– Synchronized with the primary database by

transforming the data in the redo received from the primary database into SQL statements and then executing the SQL statements

Types of Standby DatabasesPhysical Standby DatabaseA physical standby database is physically identical to the primary database, with on-disk database structures that are identical to the primary database on a block-for-block basis. The physical standby database is updated by performing recovery using redo data that is received from the primary database. The physical standby database can be either recovering data or open for read-only reporting.Logical Standby DatabaseA logical standby database is logically identical to the primary database. The logical standby database is kept synchronized with the primary database by transforming the data in the redo received from the primary database into SQL statements and then executing the SQL statements on the standby database. This is done with the use of LogMiner technology on the redo log information received from the primary database. The tables in a logical standby database can be used simultaneously for recovery and for other tasks such as reporting, summations, and queries.For more information on LogMiner, refer to Oracle Database Utilities.



Oracle Data Guard Broker Framework

CLI management client

Enterprise Manager

Repository

Primarydatabase

DataGuardbroker

Oracle Management

Server

DataGuardbroker

Agent

Standbydatabase

Agent

Oracle Data Guard BrokerThe Oracle Data Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations. After the broker creates the Data Guard configuration, the broker monitors the activity, health, and availability of all systems in the Data Guard configuration.Enterprise Manager provides a Web-based interface that combines with the broker's centralized management and monitoring capabilities so that you can easily view, monitor, and administer primary and standby databases in a Data Guard configuration.You can also use the Data Guard command-line interface (CLI) to control and monitor a Data Guard configuration. You can perform most of the activities that are required to manage and monitor the databases in the configuration from the CLI prompt (DGMGRL) or in scripts.



Types of Services

There are three types of services provided with Data Guard:• Log transport services• Log apply services

– Redo Apply– SQL Apply

• Role-management services

Types of ServicesThe following types of services are available with Data Guard:

• Log transport services: Control the automated transmittal of redo information from the primary database to one or more standby databases or destinations

• Log apply services: Control when and how the redo logs are applied to the standby database

- Redo Apply: Technology used for physical standby databases. Redo data is applied on the standby database by using the standard recovery techniques of an Oracle database.

- SQL Apply: Technology used for logical standby databases. The received redo data is first transformed into SQL statements, and then the generated SQL statements are executed on the logical standby database.

• Role-management services: A database operates in one of two mutually exclusive roles: primary or standby. Role-management services operate in conjunction with the log transport services and log apply services to change these roles dynamically as a planned transition (called a switchover operation) or as a result of a database failure through a failover operation.



Role Transitions: Switchover and Failover

• Oracle Data Guard supports two role-transition operations:– Switchover

– Planned role reversal– Used for OS or hardware maintenance

– Failover– Unplanned role reversal– Use in emergency– Zero or minimal data loss depending on choice

of data protection mode• Role-transition operations are not automatically

invoked.

Role Transitions: Switchover and FailoverData Guard enables you to change the role of a database dynamically by issuing SQL statements or by using either of the Data Guard broker's interfaces. Oracle Data Guard supports two role-transition operations:

• Switchover: The switchover feature provides you with the ability to switch the role of the primary database to one of the available standby databases. The chosen standby database becomes the primary database, and the original primary database then becomes a standby database.

• Failover: You invoke a failover operation when a catastrophic failure occurs on the primary database and there is no possibility of recovering the primary database in a timely manner. During a failover operation, the failed primary database is removed from the Data Guard environment, and a standby database assumes the primary database role. You invoke the failover operation on the standby database that you want to fail over to the primary role.


Role Transitions: Switchover and Failover (continued)You should not fail over to a standby database except in an emergency, because the failover operation may result in the loss of application data. After you perform a failover operation, there is no going back. This is because the original primary database is disabled and the standby database that you fail over to the primary role cannot return to the role of a standby database in the original configuration.



Data-Protection Modes

• Maximum protection• Maximum availability• Maximum performance

Data-Protection ModesData Guard provides three high-level modes of data protection that you can configure to balance cost, availability, performance, and transaction protection. You can configure the Data Guard environment to maximize data protection, availability, or performance.Maximum ProtectionThis protection mode guarantees that no data loss occurs if the primary database fails. To provide this level of protection, the redo data that is needed to recover each transaction must be written to both the local online redo log and to the standby redo log on at least one standby database before the transaction commits. To ensure that data loss does not occur, the primary database shuts down if a fault prevents it from writing its redo stream to at least one remote standby redo log. For multiple-instance Real Application Clusters (RAC) databases, Data Guard shuts down the primary database if it is unable to write the redo records to at least one properly configured database instance.


Data Protection Modes (continued)Maximum AvailabilityThis protection mode provides the highest possible level of data protection without compromising the availability of the primary database. As with maximum protection mode, a transaction does not commit until the redo needed to recover that transaction is written to the local online redo log and to at least one remote standby redo log. Unlike maximum protection mode, the primary database does not shut down if a fault prevents it from writing its redo stream to a remote standby redo log. Instead, the primary database operates in maximum performance mode until the fault is corrected and all gaps in redo log files are resolved. When all gaps are resolved, the primary database automatically resumes operating in maximum availability mode.This mode guarantees that no data loss occurs if the primary database fails, but only if a second fault does not prevent a complete set of redo data from being sent from the primary database to at least one standby database.Maximum Performance (Default)This default protection mode provides the highest possible level of data protection without affecting the performance of the primary database. This is accomplished by allowing a transaction to commit as soon as the redo data needed to recover that transaction is written to the local online redo log. The primary database’s redo data stream is also written to at least one standby database, but that redo stream is written asynchronously with respect to the commitment of the transactions that create the redo data.When network links with sufficient bandwidth are used, this mode provides a level of data protection that approaches that of maximum availability mode with minimal impact on primary database performance.



Benefits of ImplementingOracle Data Guard

• Continuous service through disasters or crippling data failures

• Complete data protection against corruptions and data loss

• Efficient use of system resources• Elimination of idle standby systems• Flexible configuration of your system to meet

business protection and recovery requirements• Centralized management

Oracle Data Guard provides the following benefits:

Benefits of Implementing Oracle Data GuardOracle Data Guard provides the following benefits:

• Continuous service: With the use of switchover and failover between systems, your business need not halt because of a disaster at one location.

• Complete data protection: Data Guard guarantees no data loss and provides a safeguard against data corruption and user errors. Redo data is validated when applied to the standby database.

• Efficient use of system resources: Standby databases can be used for reporting in addition to providing a safeguard for disaster recovery. You can use a logical standby for real-time reporting and the physical standby database for point-in-time reporting. You can also use the physical standby database for backups of the primary database.

• Elimination of idle standby systems: A standby database does not have to be idle when you implement a logical standby database. This database is open and ready for reporting at all times.

• Flexible configurations: You can use Data Guard to configure the system to your needs. With the use of protection modes and several tunable parameters, you can tailor the configuration to your needs.

• Centralized management: You can use Enterprise Manager to manage all configurations in your enterprise.



Role of Data Guard in a High Availability Architecture

RAC

ASM

Flashback technology

Datafailures

Computerfailures

Corruption

Human error

Sitefailure

Storagefailure

Oracle HARDRMAN

Data Guard

Role of Data Guard in a High Availability ArchitectureOracle Database offers many features to protect your system from common types of down time. This course focuses on the use of Data Guard. Data Guard addresses data failure and disaster recovery in high availability architectures.Real Application Clusters (RAC) enables you to build highly available and scalable database servers across multiple systems. For more information about Real Application Clusters, you can attend the Oracle Database 10g: Real Application Clusters course or review the Oracle Real Application Clusters Administrator’s Guide.Oracle Database 10g introduces the Automatic Storage Management (ASM) feature, which provides a vertically integrated file system and volume manager in the Oracle kernel. For additional information about ASM, see Oracle Database Concepts and theOracle Database Administrator’s Guide.Oracle Database 10g includes flashback technologies to address human errors, including Flashback Query, Flashback Versions Query, Flashback Transaction Query, Flashback Database, Flashback Table, and Flashback Drop. For additional information about these features, see the Oracle Database Administrator’s Guide.Oracle’s Hardware Assisted Resilient Data (HARD) is a comprehensive program designed to prevent data corruptions before they happen. Refer to Oracle High Availability Architecture and Best Practices for additional information about the HARD initiative.



Role of Data Guard in a High Availability Architecture

Datachanges

System changes

• Online schema anddata reorganization

• Partitioned tablesand indexes

• Dynamic resourceprovisioning

• Rolling patch updates• Rolling release upgrade

using Data GuardSQL Apply

Planneddown time

Role of Data Guard in a High Availability Architecture (continued)There are a number of features in Oracle Database to support planned down time that encompasses data changes. Tables can be redefined without interruption to users who are viewing or updating the data. Indexes can be added, rebuilt, or defragmented while the tables that they index are being queried or updated. See the Oracle Database Administrator’s Guide for additional information about these features.Oracle Database dynamically accommodates a number of hardware configuration changes.Patches can be applied to a RAC system in a rolling fashion.Oracle Database 10g supports the installation of database software upgrades (and the application of patchsets) in a rolling fashion by using Data Guard SQL Apply.



Oracle Data Guard and Real Application Clusters

Oracle Data Guard and Real Application Clusters are complementary and can be used together:• Real Application Clusters provides high

availability.• Oracle Data Guard provides disaster protection

and prevents data loss.

Oracle Data Guard and Real Application ClustersRAC provides the following for high availability:

• Rapid and automatic recovery from node failures or an instance crash• Increased scalability

Oracle Data Guard provides disaster protection and prevents data loss by:• Maintaining transactionally consistent copies of the primary database• Protecting against data corruption• Protecting against user errors• Not requiring expensive and complex mirroring of hardware or software

RAC is covered in greater detail in the “Using Data Guard with RAC” lesson.



Maximum Availability Architecture

RAC productiondatabase

RAC physicalstandby database

Oracle Application

Server

Oracle Application

Server

WAN traffic manager

Clients

Data Guard RAC logical

standby database

Maximum Availability ArchitectureRAC and Data Guard provide the basis for the database maximum availability architecture (MAA) solution. MAA provides a comprehensive architecture for reducing down time for scheduled outages and preventing, detecting, and recovering from unscheduled outages. The recommended MAA has two identical sites. The primary site contains the RAC database, and the secondary site contains both a physical standby database and a logical standby database on RAC.Identical site configuration is recommended to ensure that performance is not sacrificed after a failover or switchover. Symmetric sites also enable processes and procedures to be kept the same between sites, making operational tasks easier to maintain and execute.For more information about MAA, refer to the High Availability Architecture and Best Practices documentation.This course focuses on the Data Guard component of MAA.



Summary

In this lesson, you should have learned how to:• Describe the basic components of Oracle Data

Guard• Describe the differences between physical and

logical standby databases• Determine when Oracle Data Guard is an

appropriate solution in your Oracle Database configuration

• Explain the use of Data Guard in high availability architectures



Practice 1: Overview

This practice covers the following topics:• Reviewing the factors that affect planned and

unplanned down time• Reviewing the differences between physical and

logical standby databases• Reviewing the components of Oracle Data Guard


Understanding the OracleData Guard Architecture



Objectives

After completing this lesson, you should be able to do the following:• Describe the Data Guard architecture• Explain the operational requirements of Data

Guard• Describe how Data Guard processes, transports,

and applies redo logs• Describe standby database modes



Data Guard Operational Requirements: Hardware and Operating System

• The hardware can be different for the primary and standby databases.

• The operating system and platform architecture for the primary and standby databases must be the same.

• The operating system for the primary and standby databases must be the same, but the operating system releases can be different.

• If all databases are on the same system, verify that the OS allows you to mount more than one database with the same name.

Hardware and Operating System RequirementsThese are the operational requirements for Data Guard with respect to the hardware and operating system:

• The hardware for the primary and standby database systems can be different. For example, the number of CPUs, the memory size, and the storage configuration can differ.

• The operating system and platform architecture for the primary and standby databases must be the same.

• The operating system on both databases must be the same, but the operating system release does not need to be the same. Note: Standby databases can use a different directory structure from the primary database.

• If both the primary and the standby databases are on the same server, you must ensure that the operating system allows you to mount two databases with the same name on the same system simultaneously. There are certain parameters that must be specified to support this configuration, as discussed in the lesson titled “Creating a Physical Standby Database by Using SQL.”



Data Guard Operational Requirements: Oracle Database Software

• Same release of Oracle Database Enterprise Edition must be installed for all databases.

• SYSDBA privileges are required for the accounts used to manage the database instances.

• Each database must have its own control file.• Primary database must operate in ARCHIVELOG

mode.• Enable FORCE LOGGING on the primary database

before taking data file backups for standby creation.

• If any databases use ASM and/or OMF, all should use the same combination.

Oracle Database Software RequirementsThese are the operational requirements for Data Guard with respect to Oracle Database software:

• You must install the same release of Oracle Database Enterprise Edition for the primary database and all standby databases in your Data Guard configuration.

• You must have SYSDBA system privileges for the user accounts that you use to manage the primary and standby database instances. Furthermore, the SYS user must have the same password on all databases in the configuration.

• The primary database and each standby database must have their own control files.• The primary database must be configured in ARCHIVELOG mode.


Oracle Database Software Requirements (continued)• Some data definition language (DDL) statements permit the NOLOGGING clause, which

causes some database operations not to generate redo records in the database redo log. The NOLOGGING setting can speed up operations that can be easily recovered outside of the database recovery mechanisms, but it can negatively affect media recovery and standby databases. You can enable FORCE LOGGING to force the writing of redo records even when NOLOGGING has been specified in DDL statements. To protect against unlogged direct writes in the primary database that cannot be propagated to the standby database, enable FORCE LOGGING on the primary database before taking data file backups for standby creation. You should maintain the FORCE LOGGING mode as long as the standby database is active.

• If you use Oracle Automatic Storage Management (ASM) and Oracle Managed Files (OMF) in a Data Guard configuration, you should use ASM and OMF symmetrically on the primary and standby database. If any database in your Data Guard configuration uses ASM, OMF, or both, then every database in the configuration should use ASM, OMF, or both, respectively.



Oracle Data Guard: Architecture

LGWR

Primary database

transactions

Onlineredologs

ARC0

FAL

RFS

MRP or LSP

Archived redo logs

ARC0

Standbydatabase

Reports

(MRP only)

Standbyredo logs

Archived redo logs

BackupOra

cle

net

Oracle Data Guard: ArchitectureOracle Data Guard leverages the existing database redo generation architecture to keep the standby databases in the configuration synchronized with the primary database. By using the existing architecture, Oracle Data Guard minimizes its impact on the primary database.Oracle Data Guard uses several processes to achieve the automation that is necessary for disaster recovery and high availability. Some of these processes existed prior to the introduction of Data Guard; others were created specifically to support Oracle Data Guard. These processes are discussed in more detail on the next few pages.



Primary Database Flow

LGWR

Primary database

transactions

Onlineredologs

ARC0

FAL

RFS

MRP or LSP

Archived redo logs

ARC0

Standbydatabase

Reports

(MRP only)

Standbyredo logs

Archived redo logs

BackupOra

cle

net

Primary Database FlowOn the primary database, Data Guard log transport services use the following processes:

• Log writer (LGWR) process: LGWR collects transaction redo information and updates the online redo logs. In synchronous mode, it ships redo information directly to the remote file server (RFS) process on the standby database and waits for a confirmation before proceeding. In asynchronous mode, it ships the redo information directly but doesn’t wait before proceeding. In asynchronous mode, LGWR submits the network I/O request to the network server (LNSn) process for that destination.

• Archiver (ARCn) process: ARCn, or a SQL session performing an archival operation, creates a copy of the online redo logs locally for use in a primary database recovery. The ARCn process may also ship the redo stream to the RFS process while simultaneously archiving the online log. ARCn is also responsible for proactively detecting and resolving gaps on all standby databases.

• Fetch archive log (FAL) (physical standby databases only): FAL provides a client/server mechanism for resolving gaps detected in the range of archived redo logs that are generated at the primary database and received at the standby database. This process is started only when needed and shuts down as soon as it is finished. It is very likely you will not see this process running.

Note: You can configure a primary database to ship redo information by using LGWR or ARCn, but not both.



Standby Database Flow

LGWR

Primary database

transactions

Onlineredologs

ARC0

FAL

RFS

MRP or LSP

Archived redo logs

ARC0

Standbydatabase

Ora

cle

net

Reports

(MRP only)

Standbyredo logs

Archived redo logs

Backup

Standby Database FlowOn the standby database, Data Guard log apply services use the following processes:

• Remote file server (RFS) process: RFS receives redo information from the primary database. RFS can write the redo into standby redo logs or directly to archived redo logs. Note: Standby redo logs are optional. The use of standby redo logs is discussed in more detail later in the lesson.

• Archiver (ARCn) process: The ARCn process archives the standby redo logs. • Managed recovery process (MRP): For physical standby databases only, MRP applies

archived redo log information to the physical standby database. If you start the managed recovery with the SQL statement ALTER DATABASE RECOVER MANAGED STANDBYDATABASE; this foreground session performs the recovery. If you use the optional clause DISCONNECT [FROM SESSION], the MRP background process starts. If you use Data Guard broker to manage your standby databases, the broker always starts the MRPbackground process for a physical standby database.

• Logical standby process (LSP): For logical standby databases only, LSP controls the applying of archived redo log information to the logical standby database.



Standby Redo Logs

Redo from primary database

RFS ARC0

Standbyredo logs

Archivedredo logs

MRP/LSP

Standby database

Standby Redo LogsA standby redo log is used only when the database is in the standby role to store redo data received from the primary database. Standby redo logs form a separate pool of log file groups.Configuring standby redo log files is highly recommended on all standby databases in a Data Guard configuration, including the primary database to aid in role reversal.A standby redo log is required to implement:

• The maximum protection and maximum availability levels of data protection • Real-time apply • Cascaded redo log destinations

Standby redo logs are recommended for maximum performance data protection mode. Unless you are using the real-time apply feature, standby redo logs must be archived before the data can be applied to the standby database. The standby archival operation occurs automatically.Note: The real-time apply feature is discussed in more detail later in this lesson.



Data Guard Redo Apply: Architecture

Physical standby database

Primary database

Productiondatabase

Physical standbydatabase

Redoapply

Redo stream

Redotransport

Backup

Data Guard Redo Apply: ArchitectureThe Data Guard physical standby Redo Apply architecture consists of:

• A production (primary) database, which is linked to one or more standby databases (up to nine) that are identical copies of the production database

- The limit of nine standby databases is imposed by the LOG_ARCHIVE_DEST_n parameter. In Oracle Database 10g, the maximum number of destinations is 10. One is used as the local archive destination, leaving the other nine for uses such as the standby database. Note: You can use the Cascaded Redo Log Destinations feature to incorporate more than nine standby databases in your configuration. Refer to the “Other Considerations for Oracle Data Guard” lesson for additional information about this feature.

- The primary database is open and active. The standby databases are either in recovery mode or open read-only, but not both.


Data Guard Redo Apply: Architecture (continued)• The standby database, which is updated by redo that is automatically shipped from the

primary database. The redo can be shipped because it is generated or archived on the primary database.

- Redo is applied to each standby database by using standard Oracle recovery techniques.

- During planned down time, you can perform a switchover to a standby database.- When a failure occurs, you may fail over to one of the standby databases. - The physical standby database can also be used to back up the primary database.



Data Guard SQL Apply: Architecture

Primarydatabase

Redo transport

Transform redo information into

SQL

SQL Apply

Reports

Productiondatabase

Logical standbydatabase

Logical standby database

Data Guard SQL Apply: ArchitectureIn a logical standby database configuration, Data Guard SQL Apply uses redo information shipped from the primary system. However, instead of using media recovery to apply changes (as in the physical standby database configuration), archived redo log information is transformed into equivalent SQL statements by using LogMiner technology. These SQL statements are then applied to the logical standby database. The logical standby database is open in read/write mode and is available for reporting capabilities.



Redo records

LCRLCR

:

Shared pool

Transaction groups

Transactions sorted in

dependency order

Log Mining

Apply processing

Logical change records not grouped into transactions

Transactions to be applied

Reader Preparer Builder

AnalyzerCoordinatorApplier

Data files

Redo data from primary database

SQL Apply Process: Architecture

SQL Apply Process: ArchitectureSQL Apply uses a collection of parallel execution servers and background processes that apply changes from the primary database to the logical standby database as follows:

• The reader process reads redo records from the archived redo log files. • The preparer processes convert the block changes into table changes or logical change

records (LCRs). At this point, the LCRs do not represent any specific transactions.• The builder process assembles completed transactions from the individual LCRs.• The analyzer process examines the records, possibly eliminating transactions and

identifying dependencies between the different transactions. • The coordinator process (LSP):

- Assigns transactions - Monitors dependencies between transactions and coordinates scheduling- Authorizes the commitment of changes to the logical standby database

• The applier process: - Applies the LCRs to the database- Asks the coordinator process to approve transactions with unresolved dependencies - Commits the transactions



Real-Time Apply

RFS

Standbyredo log

files

MRP or LSP

ARC0

Primary database

Standby database

Archivedredo log

files

Real-Time ApplyWhen you enable the optional real-time apply feature, log apply services apply the redo data from standby redo log files in real time (at the same time the log files are being written to) as opposed to recovering redo from archived redo log files when a log switch occurs. If for some reason the apply service is unable to keep up (for example, if you have a physical standby in READ ONLY mode for a period of time), then the apply service automatically goes to the archive log files as needed. The apply service also tries to catch up and go back to reading the standby redo log files as soon as possible.Real-time application of redo information provides a number of benefits, including quicker switchover and failover operations, instantly up-to-date results after you change a physical standby database to read-only, up-to-date reporting from a logical standby database, and the ability to leverage larger logs files.Having larger log files with real-time apply is desirable because the apply service stays with a log longer and the overhead of switching has less impact on the real-time apply processing.The RECOVERY_MODE column of the V$ARCHIVE_DEST_STATUS view contains the value MANAGED REAL TIME APPLY when log apply services are running in real-time apply mode.


Real-Time Apply (continued)If you define a delay on a destination (with the DELAY attribute) and use real-time apply, the delay is ignored.For physical standby databases, the managed recovery process (MRP) applies the redo from the standby redo log files after the remote file server (RFS) process finishes writing. To start real-time apply for a physical standby database, issue the following command:

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE;

For logical standby databases, the logical standby process (LSP) applies the redo from the standby redo log files after the RFS process finishes writing. To start real-time apply for a logical standby database, issue the following command:

ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE;

Note: Standby redo log files are required for real-time apply. It is highly recommended that you have one more standby redo log group than the number of online log groups on the primary database.Real-time apply is supported by the broker.



Setting the DB_UNIQUE_NAME Parameter

DB_UNIQUE_NAME = SF1_DB

San Francisco

SF1_DB

Setting the DB_UNIQUE_NAME ParameterData Guard identifies all the databases in its configuration by using the DB_UNIQUE_NAMEinitialization parameter. Choose a unique name for each database and assign it with this parameter. The DB_UNIQUE_NAME value must remain constant for a given database. Therefore, you should choose names that are easy for you to remember and identify, and you should not change the names after you have assigned them. Each DB_UNIQUE_NAME value can be up to 30 characters long and must be the same for all instances in a RAC database. The default is the database name. If you use Enterprise Manager to create a standby database, it sets this to a unique value for the new standby database. Note: DB_UNIQUE_NAME replaces LOCK_NAME_SPACE, which is now deprecated. DB_UNIQUE_NAME takes precedence over LOCK_NAME_SPACE. If you still use LOCK_NAME_SPACE, it will not halt the starting of your instance.



Specifying Role-Based Destinations

Primarydatabase

Standbydatabase

LOG_ARCHIVE_DEST_2= location= "/u01/app/oracle/oradata/orcldg2/arc", valid_for=(STANDBY_LOGFILE,STANDBY_ROLE)DB_UNIQUE_NAME = HRDB2

Not used

Specifying Role-Based DestinationsThe VALID_FOR attribute of the LOG_ARCHIVE_DEST_n initialization parameter allows you to identify exactly when the archive destination is to be used, as well as for which type of log file it is used. The attribute uses a keyword pair to identify the source of the archival as well as the database role.In the example in the slide, there is a destination on the standby database and the primary database defined with the VALID_FOR setting shown. This destination is only to be used on the standby database after a switchover, when the standby becomes a primary. The destination on the old primary is ignored when it becomes a standby. You supply two values for the VALID_FOR attribute: archival_source and database_role.The archival_source keywords are the following:• ONLINE_LOGFILE: This destination is used only when archiving online redo log files.• STANDBY_LOGFILE: This destination is used only when archiving standby redo log files

or receiving archive logs from another database. • ALL_LOGFILES: This destination is used when archiving either online or standby redo

log files.


Specifying Role-Based Destinations (continued)The database_role keywords are the following:• PRIMARY_ROLE: This destination is used only when the database is in the primary

database role.• STANDBY_ROLE: This destination is used only when the database is in the standby

(logical or physical) role.• ALL_ROLES: This destination is used when the database is in either the primary or

standby (logical or physical) role.Note: Because the keywords are unique, the archival_source and database_rolevalues can be specified in any order. For example, VALID_FOR=(PRIMARY_ROLE,ONLINE_LOGFILE) is functionally equivalent to VALID_FOR=(ONLINE_LOGFILE,PRIMARY_ROLE).Also, if you are using the SERVICE keyword with the VALID_FOR attribute, you must specify the DB_UNIQUE_NAME keyword as well.



Combinations for VALID_FOR

ValidValidValidALL_LOGFILES, ALL_ROLES

ValidValidIgnoredALL_LOGFILES, STANDBY_ROLE

IgnoredIgnoredValidALL_LOGFILES, PRIMARY_ROLE

ValidValidIgnoredSTANDBY_LOGFILE, ALL_ROLES

ValidValidIgnoredSTANDBY_LOGFILE,STANDBY_ROLE

Ignored

Ignored

Ignored

Physical

ValidValidONLINE_LOGFILE, ALL_ROLES

ValidIgnoredONLINE_LOGFILE, STANDBY_ROLE

IgnoredValidONLINE_LOGFILE, PRIMARY_ROLE

LogicalPrimaryCombination

Combinations for VALID_FORIn the table, the word Valid means that the archive log destination is used in a database that is in the role defined by the column heading. The Ignored value means the archive log destination is not appropriate and a destination of this type is ignored. An ignored destination does not generate an error.ALL_LOGFILES, ALL_ROLES is not a recommended setting for a logical standby for any destination. Because a logical standby is an open database that is creating its own redo, there is a real possibility of having the log files overwrite each other. This gives you a system that is unrecoverable and/or unable to keep synchronized with the primary database.There is only one invalid combination: STANDBY_LOGFILE, PRIMARY_ROLE. If this is specified, it causes an error for all database roles. If this is set, you receive the following error at startup:

ORA-16026: The parameter LOG_ARCHIVE_DEST_n contains an invalid attribute value

Note: Both the single and plural forms of the keywords are valid. For example, you can specify either PRIMARY_ROLE or PRIMARY_ROLES, and ONLINE_LOGFILE or ONLINE_LOGFILES.



Identifying Destination Settings

SQL> SELECT DEST_ID,VALID_TYPE,VALID_ROLE,VALID_NOW

2 FROM V$ARCHIVE_DEST;

DEST_ID VALID_TYPE VALID_ROLE VALID_NOW

------- --------------- ------------ --------------

1 ONLINE_LOGFILE ALL_ROLES YES

2 STANDBY_LOGFILE STANDBY_ROLE YES

3 ALL_LOGFILES ALL_ROLES UNKNOWN








11 ALL_LOGFILES ALL_ROLES YES

11 rows selected.

Identifying Destination SettingsThe VALID_NOW column in V$ARCHIVE_DEST indicates whether or not the archive log destination is used. The column values are the following:• YES: This value indicates the archive log destination is appropriately defined for the

current database role• WRONG VALID_TYPE: This value indicates that the archive log destination is

appropriately defined for the current database role but cannot be used. For example, LOG_ARCHIVE_DEST_2 is set to (STANDBY_LOGFILES,STANDBY_ROLE), but WRONG VALID_TYPE is returned because this standby destination does not have a standby redo log implemented.

• WRONG VALID_ROLE: This value indicates that the archive log destination is not appropriately defined for the current database role. For example, LOG_ARCHIVE_DEST_3 is set to (ONLINE_LOGFILES,STANDBY_ROLE), but WRONG VALID_ROLE is returned because this destination is currently running in the primary database role.

• UNKNOWN: This value indicates that the archive log destination is not defined.The VALID_TYPE and VALID_ROLE columns are the respective values from the VALID_FORattribute that is specified for each archive log destination.



Standby Redo Log Configuration

Redo shipment

RFS

Standbyredo logs

Onlineredo logs

Primarydatabase

Standbydatabase

Standby Redo Log ConfigurationYou must create at least the same number of standby redo log files as are contained on the primary database. It is highly recommended that you have one more standby redo log group than you have online redo log groups as the primary. In addition, the files must be the same size or larger than the primary database’s online redo logs. If your online redo log files are of different sizes, the RFS process automatically uses the same size standby redo log as the online redo log file.The RFS process writes to an archive redo log file if any of the following conditions are met:

• There are no standby redo logs.• It cannot find the same size standby redo log as the incoming online redo log file.• All of the standby redo logs of the correct size have not yet been archived.



Number of Standby Redo Logs

The following clauses of the CREATE DATABASEstatement affect the number of redo logs that you can create:• MAXLOGFILES: Maximum number of groups of

standby redo logs and online redo logs per database

• MAXLOGMEMBERS: Maximum number of members per group

Number of Standby Redo LogsThe following clauses limit the number of standby redo log groups that you can add to a database:

• The MAXLOGFILES clause of the CREATE DATABASE statement for the primary database determines the maximum number of groups of standby redo logs and online redo log groups per database. The sum of online log groups and standby redo log groups must be equal to or less than MAXLOGFILES.

• The MAXLOGMEMBERS clause of the CREATE DATABASE statement that is used for the primary database determines the maximum number of members per group.

The only way to override the limits that are specified by the MAXLOGFILES and MAXLOGMEMBERS clauses is to re-create the primary database or the control file.See Oracle Database SQL Reference and your operating system–specific Oracle documentation for the default and allowed values of the MAXLOGFILES and MAXLOGMEMBERS clauses.



Using SQL to Add Standby Redo Logs

• Use the ALTER DATABASE statement to create the standby redo log files:

• Add members to a group with the following statement:

• View information about the groups as follows:

SQL> ALTER DATABASE ADD STANDBY LOGFILE MEMBER 2 '/oracle/dbs/log2b.rdo' TO GROUP 2;

SQL> ALTER DATABASE ADD STANDBY LOGFILE2 ('/oracle/dbs/log1c.rdo',3 '/oracle/dbs/log2c.rdo') SIZE 500K;

SQL> SELECT * FROM V$LOGFILE 2 WHERE TYPE = 'STANDBY';

Using SQL to Add Standby Redo LogsYou can create standby redo logs by using the ADD STANDBY LOGFILE clause of the ALTERDATABASE statement. Although standby redo logs are used only when the database is operating in the standby role, you should create standby redo logs on the primary database so that switching roles does not require additional DBA intervention.To verify that standby redo logs have been created, query V$STANDBY_LOG or V$LOGFILEwith SELECT * FROM V$LOGFILE WHERE TYPE = 'STANDBY';.The standby redo log status is shown as ACTIVE or UNASSIGNED.The following is an example of output from V$STANDBY_LOG:

SQL> SELECT GROUP#,STATUS,FIRST_CHANGE# 2 FROM V$STANDBY_LOG;

GROUP# STATUS FIRST_CHANGE#---------- ---------- -------------

3 ACTIVE 1445454 UNASSIGNED 05 UNASSIGNED 0



Using Enterprise Managerto Add Standby Redo Logs

Using Enterprise Manager to Add Standby Redo LogsWhen you create a standby configuration with Enterprise Manager, it recommends a configuration of standby redo logs. This recommendation includes creating the standby redo logs on the primary database as well as on any standby databases in the configuration.Configuring standby redo logs is covered in more detail in the lesson titled “Creating a Configuration with Enterprise Manager.”



Standby Database Modes

You can maintain the standby data in one of the following modes:• For physical standby databases

– Redo Apply– Open read-only mode

• For logical standby databases– Open read/write mode

Standby Database ModesYou can use log apply services to maintain your physical standby database in one of the following modes:

• Redo Apply: In this mode, log transport services archive the logs to the standby database, and log apply services automatically apply these logs. The database is in the MOUNT state; no reads of the data are possible.

• Open read-only mode: If you want to use the standby database for reporting purposes,then open it in read-only mode in a Data Guard environment. Log apply services cannotapply archived redo logs to the standby database when it is in this mode, but the primary database continues to ship redo to the standby database.

You can easily change between managed recovery mode and read-only mode. In most implementations of a Data Guard environment, you may want to make this transition at various times so that you can do one of the following:

• Update a physical standby database that is used primarily for reporting• Ensure that data is correctly applied to a physical standby database that is used primarily

for disaster protection


Standby Database Modes (continued)• Open read/write mode: In this mode, log apply services continue to manage the

application of log information from archived redo logs. In addition, the database is open for reporting.

The logs are being applied to the logical standby while users are allowed to perform queries on the tables that are being updated by the log apply service. Users are not allowed to perform DML on the tables in the schemas that the log apply service is updating. However, users can modify database objects in other schemas that are not being maintained by the log apply service.



Summary

In this lesson, you should have learned how to describe the following:• Data Guard architecture processes• Operational requirements of a Data Guard

environment• How Data Guard processes, transports, and

applies redo logs• Modes of standby databases and when to use

each mode



Practice 2-1: Overview(Architecture)

This practice covers the following topics:• Reviewing the Oracle Data Guard architecture• Reviewing the processes that Data Guard uses to

transport and apply redo logs• Reviewing the modes that are used to recover a

primary database



Practice 2-2: Overview(Installing the Oracle Management Agent)

This practice covers the following topics:• Installing the Oracle Management Agent• Configuring monitoring credentials for your

database



Practice 2-3: Overview(Configuring Your Primary Database)

This practice covers the following topics:• Reviewing your primary database configuration • Configuring your primary database in preparation

for creating a Data Guard configuration


Data Guard Brokerand Enterprise Manager



Objectives

After completing this lesson, you should be able to do the following:• Describe the Data Guard broker architecture• Describe the Data Guard broker components• Explain the benefits of the Data Guard broker• Explain Data Guard broker configurations• Use Enterprise Manager to manage your Data

Guard configuration• Invoke DGMGRL to manage your Data Guard

configuration



Features of Data Guard Broker

• The Data Guard broker is a distributed management framework.

• The broker automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations.

• With the broker, you can perform all management operations locally or remotely through easy-to-use interfaces: – Oracle Enterprise Manager 10g Grid Control– A command-line interface: DGMGRL

Features of Data Guard BrokerThe Oracle Data Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations. The following are some of the operations that the broker automates and simplifies:

• Automated creation of Data Guard configurations incorporating a primary database, a new or existing (physical or logical) standby database, log transport services, and log apply servicesNote: Any of the databases might be RAC databases.

• Adding up to eight additional new or existing (physical or logical, RAC or non-RAC) standby databases to each existing Data Guard configuration, for a total of one primary database, and from one to nine standby databases in the same configuration

• Managing an entire Data Guard configuration (including all databases, log transport services, and log apply services) through a client connection to any database in the configuration

• Invoking switchover or failover with a single command to initiate and control complex role changes across all databases in the configuration

• Monitoring the status of the entire configuration, capturing diagnostic information, reporting statistics such as the log apply rate and the redo generation rate, and detecting problems quickly with centralized monitoring, testing, and performance tools



Data Guard Broker: Components

• Client-side:– Oracle Enterprise Manager 10g Grid Control– DGMGRL (command-line interface)

• Server-side: Data Guard monitor– DMON process– Configuration files

Data Guard Broker: ComponentsThe Oracle Data Guard broker consists of components that reside on the client and the server in the configuration.On the client, you can use the following Data Guard components to define and manage a configuration:

• Oracle Enterprise Manager• DGMGRL, which is the Data Guard command-line interface (CLI)

On the server, Data Guard monitor is a broker component that is integrated with the Oracle database. Data Guard monitor comprises the Data Guard monitor process (DMON) and broker configuration files, with which you can control the databases of that configuration, modify their behavior at run time, monitor the overall health of the configuration, and provide notification of other operational characteristics.The configuration file contains profiles that describe the states and properties of the databases in the configuration. Associated with each database are various properties that the DMON process uses to control the database’s behavior. The properties are recorded in the configuration file as a part of the database’s object profile that is stored there. Many database properties are used to control database initialization parameters related to the Data Guard environment.



Data Guard Broker: Configurations

The most common configuration is a primary database at one location and a standby database at another location.

Chicago

Primary site

Boston

Standby site

Oracle Net

Data Guard Broker: ConfigurationsA Data Guard configuration consists of one primary database and up to nine standby databases. The databases in a Data Guard configuration are typically dispersed geographically and are connected by Oracle Net.A Data Guard broker configuration is a logical grouping of the primary and standby databases in a Data Guard configuration. The broker’s DMON process configures and maintains the broker configuration components as a unified group of resource objects that you can manage and monitor as a single unit. When you enter a command through Enterprise Manager or the CLI, the appropriate DMON process does the following:

• Carries out your request on its local database resource object and site object • Updates the broker configuration file • Communicates with the DMON process on the other site



Data Guard Broker: Management Model

Data Guard Broker Configuration

Primary database

Broker-controlled databases

Standby databaseStandby database




Standby database

Instances Instances

Data Guard Broker: Management ModelThe Data Guard broker performs operations on logical objects:

• Configuration of databases• A single database

A broker configuration consists of:• A configuration object: A named collection of database profiles. A database profile is a

description of a database object, including its current state, current status, and properties. • Database objects: Objects corresponding to primary or standby databases • Instance objects: A database object may be comprised of one or more instance objects if it

is a RAC database.The broker supports one or more Data Guard configurations, each of which includes a profile for one primary database as well as profiles for up to nine physical, logical, RAC or non-RAC standby databases.



Primary site

Standby site 9Standby site 2

Data Guard Broker: ArchitectureGraphical user interface

orcommand-line interface

DMON

Archivedredo logs

Onlineredo logs

Standby site 1

OracleNet

Standbyredo logs Archived

redo logs

Logapply

services

Data Guard Configuration

Logtransportservices

Primary database

DMON

Configurationfiles

Configurationfiles Standby

database

Data Guard Broker: ArchitectureThe Data Guard broker helps you create, control, and monitor a Data Guard configuration. This configuration consists of a primary database that is protected by one or more standby databases. After the broker has created the Data Guard configuration, the broker monitors the activity, health, and availability of all systems in the Data Guard configuration.The Data Guard monitor process (DMON) is an Oracle background process that runs on every site that is managed by the broker. When you start the Data Guard broker, a DMON process is created.When you use Enterprise Manager or the Data Guard command-line interface (CLI), the DMONprocess is the server-side component that interacts with the local instance and the DMONprocesses that are running on other sites to perform the requested function. The DMON process is also responsible for monitoring the health of the broker configuration and for ensuring that every site has a consistent copy of the configuration files in which the DMON process stores its configuration data. There are two multiplexed versions of the configuration file on each site.



Life Cycle of a Broker Configuration

Createconfiguration

Enableconfiguration

Make state orrole changes

Update databaseproperties

Monitor and tuneconfiguration

Life Cycle of a Broker ConfigurationYou can use the Add Standby Database Wizard in Enterprise Manager to add an existing standby database to the configuration or create a new standby database and add it to the configuration. The standby database can be either a physical or a logical database.Note: If you are creating a new database, it must be a non-RAC database.If you are using the CLI, the primary database and standby database must already exist. You must construct the standby database from backups of the primary database control files and data files, and then prepare it for recovery.One way to think of this life cycle is in the context of creating and staging a play. In the “create configuration” phase, you define the actors (resources) and the roles they play (primary or standby), as well as where they should be on the stage (the site).When you have made all your decisions and preparations, you go to opening night for the show’s debut (“enable configuration”).During the run of the show, changes may be required because the actor playing the main character falls ill (“make state or role changes,” in which a standby becomes primary) or because your show is in a new theater (“update database properties”). And as the director, you constantly watch to make sure the play maintains your standards, so you make modifications as needed (“monitor and tune configuration”).



Data Guard Broker: Requirements

• Enterprise Edition of Oracle Database 10g Release 1• Single-instance or multi-instance environment• COMPATIBLE must be set to 9.2.0 or higher for

primary and standby databases.• Oracle Net network files must be configured for

databases that you add to the configuration.• LOCAL_LISTENER on each instance must resolve to

an address that is reachable by all members.• GLOBAL_DBNAME attribute must be set to a

concatenation of: db_unique_name_DGMGRL.db_domain

Data Guard Broker: RequirementsTo use the Data Guard broker, you must comply with the following requirements:

• You must use the Enterprise Edition of Oracle Database 10g Release 1.• You can use a single-instance or multi-instance environment.• You must set the COMPATIBLE initialization parameter to 9.2.0 or higher for the primary

and standby databases.• Enterprise Manager automatically configures the Oracle Net network files when it creates a

standby database. If you configure an existing standby database in the broker configuration, you must configure the network files. You must use TCP/IP protocol.

• The value of the LOCAL_LISTENER initialization parameter on each instance that is part of your Data Guard broker configuration must resolve to a listener address that is reachable by all members of the configuration.

• To enable the Data Guard broker CLI to restart instances during the course of broker operations, a service with a specific name must be statically registered with the local listener of each instance. The value of the GLOBAL_DBNAME attribute must be set to a concatenation of db_unique_name_DGMGRL.db_domain.

Note: Oracle Enterprise Manager 10g can manage a 9.2 Data Guard configuration.



Data Guard Broker: Requirements

• DG_BROKER_START = TRUE

• The primary database must be in ARCHIVELOGmode.

• All databases must be in MOUNT or OPEN mode.• Configure DG_BROKER_CONFIG_FILEn for any

RAC databases.• START_OPTIONS for any RAC databases must be

set to MOUNT in the Oracle Cluster Repository (OCR).

Data Guard Broker: Requirements (continued)• You must set the DG_BROKER_START initialization parameter to TRUE. This enables the

DMON process. Note: Enterprise Manager sets this parameter automatically.

• The primary database must be in ARCHIVELOG mode.• Any database that is managed by the broker (including, for a RAC database, all instances

of the database) must be mounted or open. The broker cannot start an instance.• If any database in your configuration is a RAC database, you must configure the

DG_BROKER_CONFIG_FILEn initialization parameters for that database so that they point to the same shared files for all instances of that database. You cannot use the default values for these parameters. Note: The shared files could be files on a cluster file system, if available, or on raw devices.

• If any database in your configuration is a RAC database, the START_OPTIONS for that database must be set to MOUNT in the Oracle Cluster Repository (OCR) using SRVCTL, as follows:SRVCTL ADD DATABASE -d <db_unique_name> -o <$ORACLE_HOME> -s MOUNT

orSRVCTL MODIFY DATABASE -d <db_unique_name> -o <$ORACLE_HOME> -s MOUNT



Data Guard Broker and the SPFILE

• You must use a server parameter file (SPFILE) for initialization parameters.

• Using the SPFILE enables the Data Guard broker to keep its configuration file and the database SPFILE consistent.

• If you use the broker, use Enterprise Manager or DGMGRL to update database parameter values.

Data Guard Broker and the SPFILETo ensure that the broker can update the values of parameters in both the database instance itself and in the configuration file, you must use the persistent server initialization parameter file (SPFILE) to control static and dynamic initialization parameters. Use of the SPFILE gives the broker a mechanism that enables it to reconcile property values that you have selected when using the broker with any related initialization parameter values that are recorded in the SPFILE. Also, the SPFILE permits persistent Data Guard settings, so that Data Guard continues to work even after the broker is disabled.When you set definitions or values for database properties in the broker configuration, the broker records the change in the configuration file and also propagates the changes to the related initialization parameters in the SPFILE file in the Data Guard configuration.When the configuration is enabled, the broker keeps the database property values in the Data Guard configuration file consistent with the values of the database initialization parameters in the SPFILE.Even when the configuration is disabled, you can update database property values through the broker. The broker retains the property settings (without validating the values) and updates the database initialization parameters in the SPFILE and the in-memory settings the next time you enable the broker configuration.


Data Guard Broker and the SPFILE (continued)For dynamic initialization parameters, the broker keeps the value of the database parameter consistent in the System Global Area (SGA) for the instance, in the Data Guard configuration files, and in the SPFILE.For static initialization parameters, the value in the SGA may differ from what is in the configuration files and in the SPFILE. Typically, the broker reconciles the differences by updating all parameter and property values the next time the database instance is stopped and restarted.Note: When using the broker (with Enterprise Manager or the CLI), do not attempt to manually set the parameters the broker controls. If you set them manually, one of two things happens. Either you render your configuration inoperable, or the broker simply resets the parameter to the setting it has recorded at the next opportunity. If you want to change a parameter value, you must change it by using one of the broker interfaces.



Data Guard Monitor: DMON Process

• Server-side background process• Part of each database instance in the

configuration• Created when you start the broker• Performs requested functions and monitors the

resource• Communicates with other DMON processes in the

configuration• Updates the configuration file

Data Guard Monitor: DMON ProcessThe Data Guard monitor comprises two components: the DMON process and the configuration file.The Data Guard Monitor process (DMON) is an Oracle background process that is part of each database instance managed by the broker. When you start the Data Guard broker, a portion of the SGA is allocated and a DMON process is created. The amount of memory allocated is typicallyless then 50 KB per site; the actual amount on your system varies.When you use Enterprise Manager or the CLI, the DMON process is the server-side component that interacts with the local instance and the DMON processes running on other sites to perform the requested function.The DMON process is also responsible for monitoring the health of the broker configuration and for ensuring that every database has a consistent copy of the broker configuration files in which the DMON process stores its configuration data.



Data Guard Monitor: Configuration File

• Automatically created and named using a default path name and file name when the broker is started

• Override default path name and file name by setting DG_BROKER_CONFIG_FILEn

• Two files at each managed site• Managed automatically by the DMON process• Default names are operating system–specific:

– Default names for Unix and Linux: dr1<SID>.datand dr2<SID>.dat

– Default location for Unix and Linux: ORACLE_HOME/dbs

– Default location for Windows: ORACLE_HOME\database

Data Guard Monitor: Configuration FileThe DMON process maintains persistent configuration data about all databases in the broker configuration in a broker configuration file. Every database that is part of the Data Guard broker configuration has two broker configuration files that are maintained and synchronized for each database in the broker configuration. One of the files is in use and the other acts as a backup. The configuration files are binary files and cannot be edited.When the broker is started for the first time, the configuration files are created and named automatically by using a default name that is specific to the operating system. You can override this default name by setting the DG_BROKER_CONFIG_FILEn initialization parameters. You can also change the configuration file names dynamically by issuing the ALTER SYSTEM SQL statement.The configuration files contain entries that describe the state and properties of the databases in the configuration. For example, the files record the databases that are part of the configuration, the roles and properties of each of the databases, and the state of each of the databases in the configuration. Two files are maintained so that there is always a record of the last known valid state of the configuration. The broker uses the data in the configuration file to configure and start the databases, control each database’s behavior, and provide information to the CLI and Enterprise Manager.



Benefits of Using the Data Guard Broker

• Enhances the high-availability, data-protection, and disaster-protection capabilities inherent in Oracle Data Guard by automating both configuration and monitoring tasks

• Streamlines the process for any one of the standby databases to replace the primary database and take over production processing

• Helps you to logically define and create a Data Guard configuration consisting of a primary database and a standby database

• Enables easy configuration of additional standby databases

Benefits of Using the Data Guard BrokerBy automating the tasks required to configure and monitor a Data Guard configuration, the broker enhances the high-availability, data-protection, and disaster-protection capabilities that are inherent in Oracle Data Guard.If the primary database fails, the broker streamlines the process for any one of the standby databases to replace the primary database and take over production processing.The broker helps you to logically define and create a Data Guard configuration consisting of a primary database and a (physical or logical, RAC or non-RAC) standby database. The broker enables easy configuration of additional standby databases. After you create a Data Guard configuration consisting of a primary and standby database, you can add up to eight standby databases (new or existing, physical or logical) to each Data Guard configuration.



Benefits of Using the Data Guard Broker

• Provides simplified, centralized, and extended management

• Automates switchover and failover to a specified standby database in the broker configuration

• Automatically communicates between the databases in a Data Guard configuration using Oracle Net Services

• Provides built-in validation that monitors the health of all of the databases in the configuration

Benefits of Using the Data Guard Broker (continued)The broker provides simplified, centralized, and extended management.The broker automates switchover and failover to a specified standby database in the broker configuration. The broker automatically communicates between the databases in a Data Guard configuration using Oracle Net Services. The database can be local or remote, connected by a LAN or geographically dispersed over a WAN.The broker provides built-in validation that monitors the health of all of the databases in the configuration.



Data Guard Broker Interfaces

• Oracle Enterprise Manager 10g Grid Control:– Contains wizards to simplify creating and managing

standby databases• Command-line interface (CLI):

– Started by entering DGMGRL at the command prompt where the Oracle server is installed

– Enables you to control and monitor a Data Guard configuration from the CLI prompt or in scripts

Data Guard Broker InterfacesOracle Enterprise Manager automates and simplifies the management of a Data Guard configuration.Oracle Enterprise Manager 10g Grid Control includes the following Data Guard features:

• Wizard-driven creation of standby databases• Wizard-driven creation of a broker configuration based on an existing primary and standby

database• Complete monitoring and proactive event reporting through e-mail or pagers• Simplified control of the databases through their potential states. For example, with

Enterprise Manager you can take a database offline, put it online, start or stop the log transport services, start or stop the log apply services, place a standby database in read-only mode, and so on.

• “Pushbutton” switchover and failover: Grid Control enables you to execute a switchover or failover between a primary and a standby database by simply clicking a button.


Data Guard Broker Interfaces (continued)The DGMGRL command-line interface (CLI) includes:

• Configuration and setup tasks• Management and control of the configuration• Commands to check the status and health of the configuration• Commands to execute role changes

For additional information about using these interfaces, see Oracle Data Guard Broker.



Using Oracle Enterprise Manager 10gGrid Control

Click Data Guard to access the Data Guard pages.

Using Oracle Enterprise Manager 10g Grid ControlAccess the Data Guard features in Grid Control by performing the following steps:

1. Click the Targets tab to go to the Targets page.2. Click Databases to go to the Databases page.3. On the Databases page, you can see a listing of all discovered databases, including the

primary database. Click the primary database to go to the primary database home page.4. Click Administration.5. Click Data Guard in the High Availability section.



Data Guard Overview Page

Data Guard Overview PageOn the Data Guard Overview page, you can:

• View the protection mode and access the page to edit the protection mode• View a summary showing the amount of data that the standby has not received• View information about the primary database• View or access pages to change information for the standby databases:

- Add a standby database to the broker configuration- Change the state or properties- Discontinue Data Guard broker control- Switch the role from standby to primary- Transition the standby database to the role of primary database

• Access pages to view performance information for the configuration and status of online redo log files for each standby database

• Perform a verification process on the Data Guard configurationYou can click Help to access information about using each page.



Enterprise Manager Metrics and Alerts

• Metrics: Units of measurement used to assess the health of your system

• Thresholds: Boundary values against which monitored metric values are compared

• Alert: Generated when a threshold is reached

Enterprise Manager Metrics and AlertsMetrics are units of measurement that are used to assess the health of your system. Each target comes with a predefined set of metrics. Metrics have thresholds associated with them.Thresholds are boundary values against which monitored metric values are compared. Some of the thresholds are predefined by Oracle; others are not.When a threshold is reached, an alert is generated. An alert is an indicator signifying that a particular condition has been encountered. An alert is triggered when one of the following conditions is true:

• A threshold is reached.• An alert has been cleared.• The availability of a monitored service changes.• A specific condition occurs. For example, an alert is triggered whenever an error message

is written to a database alert log file.Alerts are detected through a polling-based mechanism by checking for the monitored condition from a separate process at regular, predefined intervals. You can associate an alert with a notification, the automatic execution of a job, and so on.



Using Data Guard Metrics

Enterprise Manager includes the following Data Guard metrics:• Data Guard Status• Data Not Applied (MB)• Data Not Applied (log

files)• Data Not Received (MB)• Data Not Received (log

files)

Using Data Guard MetricsYou can use Enterprise Manager to monitor the status and log file activity. In addition, Enterprise Manager automatically monitors the status and archived redo log file activity on the primary and standby databases and provides the following metrics:

• Data Guard Status: Status of each database in the broker configuration• Data Not Applied (MB): Difference (in megabytes) between the last log file received and

the last log file applied on each standby database• Data Not Applied (log files): Difference (in number of archived redo log files) between

the last log file received and the last log file applied on each standby database• Data Not Received (MB): Difference (in megabytes) between the current log file on the

primary database and the last log file received on each standby database• Data Not Received (log files): Difference (in number of archived redo log files) between

the current log file on the primary database and the last log file received on each standby database

You can set up Email Services to notify you with an e-mail message if any of the metrics are triggered.Note: These metrics are seen on the primary database only.



Managing Data Guard Metrics

1. Configure notification methods.2. View the All Metrics page.3. Set or change Data Guard metric thresholds.4. View triggered metrics.

Managing Data Guard MetricsYou can specify that an e-mail notification be sent to you when a Data Guard metric is triggered. Use the following procedure to configure the notification:

1. Configure notification methods in Enterprise Manager.a. Click Setup at the top of the Database Home page.b. Click Notification Methods on the Setup page.c. Enter the appropriate information in the Mail Server section and click Apply. You

can click Test Mail Servers to verify your configuration.2. View the All Metrics page by clicking All Metrics in the Related Links section on the

Database Home page. Then view all of the Oracle Enterprise Manager metrics, including the metrics for Data Guard.

3. Set or change Data Guard metric thresholds by clicking Manage Metrics in the Related Links section on the All Metrics page to access the Manage Metrics page. You can set and change the five Data Guard metrics from the Manage Metrics page.

4. View triggered metrics: If a metric condition is triggered or a threshold value is exceeded, an alert is issued. Click Data Guard on the All Metrics page to view triggered metrics. You can click the metric and then click a particular database to see details.



Benefits of Using Enterprise Manager

• Enables you to manage your configuration using a familiar interface and event-management system

• Automates and simplifies the complex operations of creating and managing standby databases through the use of wizards

• Performs all Oracle Net Services configuration changes that are necessary to support log transport services and log apply services

• Provides a verify operation to ensure that log transport services and log apply services are configured and functioning properly

• Enables you to select a new primary database from a set of viable standby databases

Benefits of Using Enterprise ManagerManaging your Data Guard configuration with Oracle Enterprise Manager 10g Grid Control provides the following benefits:

• Enables you to manage your configuration using the familiar Enterprise Manager interface and event-management system

• Provides a wizard that automates the complex tasks involved in creating a broker configuration

• Provides the Add Standby Database Wizard to guide you through the process of adding more databases

• Performs all Oracle Net Services configuration changes that are necessary to support log transport services and log apply services across the configuration

• Provides a verify operation to ensure that log transport services and log apply services are configured and functioning properly

• Enables you to select a new primary database from a set of viable standby databases when you need to initiate a role change for a switchover or failover operation



Using the Command-Line Interfaceof the Data Guard Broker

DGMGRL> connect sys/oracleConnected.DGMGRL> show configuration verbose

ConfigurationName: ORCL_EDRSR9P1.oracle.comEnabled: YESProtection Mode: MaxPerformanceDatabases:ORCL_EDRSR9P1 - Primary databasesite1_edrsr9p1 - Physical standby databasesite2_edrsr9p1 - Logical standby database

Current status for "ORCL_EDRSR9P1.oracle.com":SUCCESS

DGMGRL CommandsThe following commands are available in DGMGRL (the Data Guard CLI). Many of these commands have additional arguments that are not described here. This is simply an overview listing.• ADD: Adds a standby database to the broker configuration• CONNECT: Connects a given username to the specified instance• CREATE: Enables you to create broker configurations• DISABLE: Enables you to disable broker control of a configuration or database so that the

object is no longer managed by the broker• EDIT: Used to edit a configuration, database, or instance• ENABLE: Enables you to enable broker control of a configuration or database• EXIT/QUIT: Exits the Data Guard CLI (DGMGRL)• FAILOVER: Performs a database failover operation in which one of the standby databases

changes to the role of primary database. This is an unplanned transition that may result in the loss of application data.

• HELP: Displays online help for the commands in DGMGRL• REMOVE: Removes a broker configuration, including all of its database profiles, a specified

standby database profile, or knowledge of an instance


DGMGRL Commands (continued)• SHOW: Displays either a brief or a detailed summary of information about the broker

configuration, database, or instance. Also can display the dependency tree and default online states for the broker configuration, as well as the configuration log or the Oracle database alert log.

• SHUTDOWN: Shuts down a currently running Oracle database instance• STARTUP: Starts an Oracle instance with several options, including mounting and opening

a database• SWITCHOVER: Performs a switchover operation in which the current primary database

becomes a standby database and the standby database to which the CLI is currently connected becomes the primary database

Note: The ALTER command has been deprecated in Oracle Database 10g. The new EDITcommand provides comparable functionality.



Summary

In this lesson, you should have learned how to:• Describe the Data Guard broker management

model• Describe the Data Guard broker architecture• Describe Data Guard broker components• Access Enterprise Manager• Invoke DGMGRL (the Data Guard CLI)


Creating a Configurationwith Enterprise Manager



Objectives

After completing this lesson, you should be able to do the following:• Enable FORCE LOGGING• Use Enterprise Manager to create a broker

configuration• Use Enterprise Manager to monitor the broker

configuration



Enabling FORCE LOGGING Mode

• Forced logging is recommended to ensure data consistency.

• FORCE LOGGING forces redo to be generated even when NOLOGGING operations are executed.

• Temporary tablespaces and temporary segments are not logged.

• FORCE LOGGING is recommended for both physical and logical standby databases.

• Issue the following command on the primary database:

SQL> ALTER DATABASE FORCE LOGGING;

Enabling FORCE LOGGING ModeFORCE LOGGING mode determines whether or not the Oracle database server logs all changes in the database, except for changes to temporary tablespaces and temporary segments. The [NO]FORCE LOGGING clause of the ALTER DATABASE command contains the following settings:• FORCE LOGGING: This setting takes precedence over (and is independent of) any

NOLOGGING or FORCE LOGGING settings that you specify for individual tablespaces and any NOLOGGING setting that you specify for individual database objects. All ongoing, unlogged operations must finish before forced logging can begin.

• NOFORCE LOGGING: Places the database in NOFORCE LOGGING mode. This is the default.

The FORCE_LOGGING column in V$DATABASE contains a value of YES if the database is in FORCE LOGGING mode.


Enabling FORCE LOGGING Mode (continued)Although the database can be placed in FORCE LOGGING mode when the database is OPEN, the mode does not change until any operation that is currently running in NOLOGGING mode has completed. Therefore, it is recommended that you enable FORCE LOGGING mode when the database is in the MOUNT state.Note: You should enable FORCE LOGGING before performing the backup operation to create the standby database, and then maintain FORCE LOGGING mode for as long as the standby database is active.



Using Enterprise Manager to Create a Broker Configuration

• Use the Add Standby Database Wizard to:– Create a broker configuration– Add a database to a broker configuration

• Primary database must be started with an SPFILE.

Using Enterprise Manager to Create a Broker ConfigurationEnterprise Manager automates the process of creating a standby database. The Add Standby Database Wizard is used to create a new broker configuration and to add databases to an existing configuration. Before you invoke the Add Standby Database Wizard, verify that the primary database instance was started with a server parameter file (SPFILE). If the instance was not started with an SPFILE, the wizard notifies you.



Creating a Configuration

Click “Add Standby Database” to start the wizard.

Creating a ConfigurationYou can access the Data Guard features in Enterprise Manager by clicking Data Guard in the High Availability section of the Administration page.If your primary database is not already in a broker configuration, an information page appears with this indication. Click the Add Standby Database link to invoke the Add Standby Database Wizard.Using the Add Standby Database Wizard, you perform the following steps:

1. Specify the backup type to use for the standby database creation.2. Specify the backup options.3. Select the Oracle home in which to create the standby database.4. Specify the location for standby database files.5. Specify standby database configuration parameters.6. Review the configuration information.


Creating a Configuration (continued)During the standby creation process, the following operations are performed:

• The control file, data files, and archived redo log files are backed up to a temporary location on the primary host.

• The backup pieces from the primary host are transferred to a temporary location on the standby host.

• Additional required files, such as initialization parameter and password, are created on the standby host.

• The control file, data files, and archived redo log files are restored to the specified locations on the standby host.

• Online log files and other files are added to the standby database as needed.• The recovered database is changed into a physical or logical standby.



Using the Add Standby Database Wizard

Using the Add Standby Database WizardThe Add Standby Database Wizard begins by asking you to select the type of standby database that you want to create. You can create a new physical or logical standby database. Or you can add an existing database, including a RAC database, to the configuration to serve as a standby database.Note: You must be connected to the primary database with SYSDBA credentials to invoke the Add Standby Database Wizard.If you choose to create a new standby database, the following conditions are verified when you click Continue:

• All databases in the configuration are using a server parameter file (SPFILE).• The primary database is in ARCHIVELOG mode.• The COMPATIBLE initialization parameter for the primary database has a setting

of 9.0 or higher.If any of these conditions are not met, the wizard returns a message indicating that you must cancel the wizard and perform the appropriate action to meet the condition.In addition, the wizard verifies that the primary database is in FORCE LOGGING mode. If it is not in FORCE LOGGING mode, a warning message appears. You can then cancel the configuration and enable FORCE LOGGING (as described earlier in this lesson).



Step 1: Specify the Backup Type

Step 1: Specify the Backup TypeYou can use the Backup Type page of the wizard to select the type of backup for creation of the standby database:

• “Perform a live backup of the primary database”: Creates a new backup using the Recovery Manager utility (RMAN)

• “Use an existing backup of the primary database”: Uses an existing backup of the primary database that was created by Data Guard during previous creation of a standby database



Step 2: Specify the Backup Options

Step 2: Specify the Backup OptionsIf you selected the “Perform a live backup of the primary database” option on the Backup Type page, you can specify a location on the primary database host to store the backup files. A default location is specified in the Working Directory Location field, or you can provide your own location. A unique subdirectory to store the backup files is created in the directory that you specify.If you intend to create additional standby databases, you can save the backup by selecting the “Retain working directory for a future standby creation” option. Otherwise, you should select the “Delete working directory after standby creation” option. Note: If you choose to retain the backup, additional space is required (as indicated on the Backup Options page). If you selected the “Use an existing backup of the primary database” option on the Backup Type page, specify the location of the backup in the Working Directory Location field. Note: This backup must have been taken by Data Guard during a previous standby database creation and must be of the same type that you are creating.Specify the operating system credentials of the user who owns the primary database Oracle server installation in the Primary Host Credentials section. Note: The credentials are preset to the host preferred credentials that are stored with the primary database preferred credentials by default.



Step 3: Select the Oracle Home – Instance Name

Step 3: Select the Oracle Home – Instance NameSpecify the instance name for your new standby database in the Standby Instance Name field, or use the default instance name that is provided. The instance name must conform to Oracle naming guidelines.Note: For a physical standby, the database name is the same as the primary. This is because a physical standby is an exact, block-by-block copy of the primary. You can make the instance name the same as the primary. However, you must make the instance name different from the primary if the standby is on the same machine as the primary.In the Standby Host Credentials section, specify the operating system credentials of the user who owns the Oracle installation in the selected Oracle home on the standby host.



Step 3: Select the Oracle Home –Oracle Home

Step 3: Select the Oracle Home – Oracle HomeThe Standby Database Oracle Home section lists all of the available Oracle homes that match the primary database version and host operating system. From this list, select the host and Oracle home for your new standby database.



Step 4: Specify the Standby Database File Locations – Access Method

Step 4: Specify the Standby Database File Locations – Access MethodThe Backup File Access section appears only when you are creating a standby database on a host other than the primary database. You must select a method to be used to make the primary backup files accessible to the standby host.

• Transfer files: If you choose to transfer files from the primary host working directory to a standby host directory, you must specify a temporary location on the standby host to store the backup files copied from the primary host. In addition, you must select the file transfer method: FTP or HTTP server. FTP is the faster of the two file transfer methods. Select the HTTP Server option if you know that the primary and/or standby host does not support FTP.

• Directly access the files: If you select this method, you must supply the network path name for the standby host. This method is appropriate when the primary host working directory location is directly accessible from the standby host via NFS, a network share, or some other network method. This option saves time and disk space because there is no file transfer to the standby host and because no temporary location is needed.



Step 4: Specify the Standby Database File Locations – File Locations

Step 4: Specify the Standby Database File Locations – File LocationsBy default, all standby database files are placed in an Oracle Optimal Flexible Architecture (OFA) directory structure when your primary and standby databases are on the same host.When your primary and standby databases are on different hosts, you can specify that you want to convert the standby files to an OFA structure or keep the file names and locations the same as the primary database. You can optionally change the locations of individual standby database files by clicking the Customize button to display the File Locations Customize page of the wizard.Data Guard automatically adds configuration information for the new standby database to the listener.ora and tnsnames.ora files in the directory that is specified in the Configuration File Location field in the Network Configuration File Location section. The default location is the network administration directory of the Oracle home for the standby database Oracle home. The default location is correct for most configurations. You can specify a different directory if you want the new standby database to be serviced by a listener running in a different Oracle home on the standby host.



Step 5: Specify Standby Database Configuration Parameters

Step 5: Specify Standby Database Configuration ParametersOn the Standby Configuration page of the wizard, you can specify configuration parameters for the standby database. The parameters that must be specified depend on whether you are adding an existing standby database, creating a new physical standby database, or creating a new logical standby database. The configuration parameters include the instance name, service provider name, target name, and standby archive location. The default values are based on corresponding primary database settings.When you create a new physical database, the following parameters must be configured:

• Database Unique Name: Specify a value for the database DB_UNIQUE_NAMEparameter. This name must be unique within the Data Guard configuration. Note: This field appears only if you are creating a new physical standby database and the primary database is an Oracle10g database.

• Target Name: Specify a name for Enterprise Manager to use for the new standby database. This name will appear in the list of database targets maintained by Enterprise Manager. This name should be the same as the database unique name.



Step 6: Review the Configuration Information

Step 6: Review the Configuration InformationThe Review page of the wizard displays a summary of your selections and lists the parameters to be used to create the new standby database.The new standby database is created in the background by an Oracle Enterprise Manager job. The name of the job that is submitted is provided at the top of the page.When you click Finish, the Processing page appears. This page tracks each step through the submission of the standby creation job. After the job submission is complete, the Data Guard Overview page appears, where you can monitor the progress of the standby creation job.



Standby Database Creation: Processing

Standby Database Creation: ProcessingYou can view the progress of the Add Standby Database process on the Processing page. On completion of the process, Oracle Enterprise Manager displays the Data Guard Overview page.The display on the Processing page differs based on whether you are adding an existing standby database or creating a new standby database. An arrow icon indicates what step is processing. When it completes, a check icon appears next to the step. The following steps appear on the Processing page:

• Creating Data Guard Configuration or Updating Data Guard Configuration: The Data Guard configuration is created during this step if it does not exist. If you are adding an existing standby database, it is added to the configuration.

• Preparing standby creation job: This step appears only if you are creating a new standby database. The standby database is actually created by an Enterprise Manager job; preliminary setup steps to prepare for job submission are accomplished in this step. You can cancel the Add Standby Database process at any point up to the completion of this step.


Standby Database Creation: Processing (continued)• Submitting standby creation job: This step appears only if you are creating a new

standby database. The Enterprise Manager job that creates the standby database in the background is submitted in this step. The Add Standby Database process cannot be canceled once this step begins.

• Adding standby database target: In this step, the standby database target in Enterprise Manager is updated with additional information denoting membership in the Data Guard configuration. This enables enhanced summary information to be displayed on the Enterprise Manager home page of the standby database.



Standby Database Creation: Progress

Click “Creation in progress” to view the job.

Standby Database Creation ProgressAfter the job is submitted, you return to the Data Guard Overview page. The Status column indicates that the standby database creation is in progress. Click the “Creation in progress” link to access the job page and monitor the progress of the creation of the standby database.



Standby Database Creation: Job Details

Standby Database Creation: Job DetailsYou can monitor creation of the standby database by viewing the details on the job progress page.



Verifying a Configuration

Verifying a ConfigurationAfter you create your configuration, you should use the Data Guard Verify operation to check the configuration. You can invoke the Verify operation by clicking Verify in the Additional Administration section of the Data Guard page. When you invoke the Verify operation, a series of validation checks is performed on the Data Guard configuration, including a health check of each database and each agent. The Verify operation does the following:

• Determines the current data protection mode settings, including the current log transport mode settings for each database and whether or not the standby redo logs are configured properly. If standby redo logs are needed for any database, a message indicates this on the Detailed Results page. You can then add the standby redo logs.

• Validates each database for the current status • Performs a log switch on the primary database (for non-RAC databases) and verifies

that the log was applied on each standby database• Checks the agent status for each database. The verify process executes a SQL*Plus job

on the agent if credentials are available. If credentials are not available to run the job, the agent is pinged instead. If any errors occur during this process, a message appears on the Detailed Results page.

• Displays the results of the Verify operation, including any errors Note: You can cancel the Verify operation at any time by clicking Cancel.



Reviewing Results of the Verify Operation

Reviewing Results of the Verify OperationYou can view the results of the Verify operation on the Detailed Results page. If any errors occur during the operation, detailed information appears on this page.



Creating Standby Redo Logs

Creating Standby Redo LogsIf standby redo log files are needed for any of the databases, a message appears. You can click OK to create the standby redo logs.As discussed in the lesson titled “Understanding the Oracle Data Guard Architecture,” standby redo logs should be configured on all databases in a configuration, including the primary database.



Viewing the Data Guard Configuration Status

Viewing the Data Guard Configuration StatusOn the Data Guard page, you can view the status of the primary database and the standby databases in a configuration.



Viewing Data Guard Performance

Viewing Data Guard PerformanceYou can click Performance Overview in the Performance section of the Data Guard Overview page to access the Performance Overview page.The Performance Overview page displays detailed performance-related statistics for the Data Guard configuration. The performance charts provide a graphical summary of all redo log activity in the configuration. You can set the collection interval (which causes the charts to be refreshed) to determine the rate of sampling of the primary database in the View Data field. The Performance Overview page displays performance information for all of the databases in the configuration as follows:

• Data Archived: Shows the amount of redo data (in megabytes) that has been archived on the primary database. Each point on the chart represents the amount of redo data that has been archived since the last time it was refreshed.

• Standby Progress Summary: Shows the approximate amount of potential data loss• Data Applied: Displays the data applied (in megabytes) on each standby database in

the configuration. Each point on the chart represents the amount of redo data that has been applied since the last time it was refreshed.


Viewing Data Guard Performance (continued)• Log Services Summary: Shows the progress of the log services. The Completed

column for the primary database indicates the percentage of the current online redo log that is filled. The Status column for the standby database typically displays “waiting for log” or “applying log.”

Note: Data is not collected for any offline or disabled databases.



Summary

In this lesson, you should have learned how to:• Enable FORCE LOGGING• Use Enterprise Manager to create a configuration• Use Enterprise Manager to monitor the

configuration




This practice covers the following topics:• Logging in to Oracle Enterprise Manager 10g

Grid Control• Using the wizard to create a Data Guard broker

configuration with a physical standby database• Verifying the configuration


Creating a Physical Standby Databaseby Using SQL



Objectives

After completing this lesson, you should be ableto use SQL commands to create a physical standby database.



Steps to Create a Physical Standby Database

1. Prepare the primary database.2. Back up the primary database.3. Copy files to the standby system.4. Set parameters on the physical standby database.5. Start the standby database.6. Configure Oracle Net Services.7. Set parameters on the primary database.8. Start the transport of redo.

Steps to Create a Physical Standby DatabasePerform the following steps to create a physical standby database by using SQL commands:

1. Prepare the primary database.2. Back up the primary database.3. Copy files to the standby system.4. Set parameters on the physical standby database.5. Start the standby database.6. Configure Oracle Net Services.7. Set parameters on the primary database.8. Start the transport of redo.



Preparing the Primary Database

• Enable FORCE LOGGING at the database level.

• Create a password file.• Set initialization parameters.• Enable archiving.

SQL> ALTER DATABASE FORCE LOGGING;

SQL> SHUTDOWN IMMEDIATE;SQL> STARTUP MOUNT;SQL> ALTER DATABASE ARCHIVELOG;SQL> ALTER DATABASE OPEN;

Preparing the Primary DatabaseFORCE LOGGING mode determines whether or not the Oracle database server logs all changes in the database, except for changes to temporary tablespaces and temporary segments. The FORCE_LOGGING column in V$DATABASE contains a value of YES if the database is in FORCE LOGGING mode.Every database in a Data Guard configuration must use a password file, and the password for the SYS user must be identical on every system for redo data transmission to succeed. For details about creating a password file, see Oracle Database Administrator’s Guide.On the primary database, you define initialization parameters that control log transport services while the database is in the primary role. There are additional parameters that you need to add that control the receipt of the redo data and log apply services when the primary database is transitioned to the standby role.If archiving is not enabled, issue the ALTER DATABASE ARCHIVELOG command to put the primary database in ARCHIVELOG mode and enable automatic archiving. See Oracle Database Administrator’s Guide for additional information about archiving. Note: It is no longer necessary to set the LOG_ARCHIVE_START initialization parameter to start automatic archiving.



Initialization Parameters on the Primary Database

DB_NAME=chicagoDB_UNIQUE_NAME=chicagoSERVICE_NAMES=chicagoLOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston)'CONTROL_FILES='/arch1/chicago/control1.ctl', '/arch2/chicago/control2.ctl'LOG_ARCHIVE_DEST_1='LOCATION=/arch1/chicago/VALID_FOR=(ALL_LOGFILES,ALL_ROLES)DB_UNIQUE_NAME=chicago'LOG_ARCHIVE_DEST_2='SERVICE=bostonVALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)DB_UNIQUE_NAME=boston'LOG_ARCHIVE_DEST_STATE_1=ENABLELOG_ARCHIVE_DEST_STATE_2=ENABLEREMOTE_LOGIN_PASSWORDFILE=EXCLUSIVELOG_ARCHIVE_FORMAT=%t_%s_%r.arc

Setting Initialization Parameters on the Primary DatabaseOn the primary database, you define initialization parameters that control log transport services while the database is in the primary role. In the example in the slide, assume that the primary database is named chicago and the standby is named boston. For each, there is an Oracle Net Services name defined. There are additional parameters you need to add that control the receipt of the redo data and log apply services when the primary database is transitioned to the standby role:FAL_SERVER=boston

FAL_CLIENT=chicago

DB_FILE_NAME_CONVERT=

'/arch1/boston/','/arch1/chicago/','/arch2/boston/','/arch2/chicago/'

LOG_FILE_NAME_CONVERT=

'/arch1/boston/','/arch1/chicago/','/arch2/boston/','/arch2/chicago/'

STANDBY_FILE_MANAGEMENT=AUTO

Specifying these initialization parameters configures the primary database to resolve gaps, converts new data file and log file path names from a new primary database, and archives the incoming redo data when this database is in the standby role.



LOG_ARCHIVE_CONFIG

• Specify the DG_CONFIG attribute to list the DB_UNIQUE_NAME for the primary database and each standby database in the Data Guard configuration.

• The LOG_ARCHIVE_CONFIG parameter also allows the following values:– SEND: Enables a database to send redo data to

remote destinations– RECEIVE: Enables the standby database to receive

redo from another database– Use the NOSEND and NORECEIVE keywords to

disable these settings.

LOG_ARCHIVE_CONFIG

Specify the DG_CONFIG attribute on the LOG_ARCHIVE_CONFIG parameter to list the DB_UNIQUE_NAME of the primary and standby databases in the Data Guard configuration. This setting enables the dynamic addition of a standby database to a Data Guard configuration that has a Real Application Clusters primary database running in either maximum protection or maximum availability mode. By default, theLOG_ARCHIVE_CONFIG parameter enables the database to send and receive redo. After a role transition, you may need to specify these settings again using the SEND, NOSEND, RECEIVE, or NORECEIVE keywords.Use the V$DATAGUARD_CONFIG view to see the current setting.Note: The LOG_ARCHIVE_CONFIG initialization parameter replaces the REMOTE_ARCHIVE_ENABLE initialization parameter, which will be deprecated in a future release. Do not specify both parameters in the same SPFILE or text initialization parameter file.



LOG_ARCHIVE_DEST_n

• Specify at least two LOG_ARCHIVE_DEST_nparameters.

• Must contain (at a minimum) one of the following:– LOCATION

– SERVICE

• LOG_ARCHIVE_DEST_STATE_n parameter for each defined destination

LOG_ARCHIVE_DEST_2='SERVICE=bostonVALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)DB_UNIQUE_NAME=boston'LOG_ARCHIVE_DEST_STATE_2=ENABLE

LOG_ARCHIVE_DEST_n

By using the various LOG_ARCHIVE_DEST_n attributes, you define most of the settings for the Data Guard configuration. The transport service is directly controlled by these settings. There are 35 different attributes that can be set for each LOG_ARCHIVE_DEST_nparameter. Most have defaults that are adequate for most configurations. See Oracle Data Guard Concepts and Administration for a compete list and description of each. You should specify at least two LOG_ARCHIVE_DEST_n parameters (where n is an integer from 1 to 10): one parameter for the required local archiving destination and another parameter for a standby location. Query the V$ARCHIVE_DEST view to see current settings of the LOG_ARCHIVE_DEST_n initialization parameter.All LOG_ARCHIVE_DEST_n parameters must contain, at a minimum, either a LOCATIONor SERVICE attribute. In addition, you must have a LOG_ARCHIVE_DEST_STATE_nparameter for each defined destination.



LOCATION and SERVICE Attributes

Each archive log destination includes one of the following attributes:• LOCATION: Specifies a valid path name• SERVICE: Specifies a valid Oracle Net Services

name referencing:– A standby database– An archive log repository– A cross-instance archival database

LOG_ARCHIVE_DEST_1='LOCATION=/arch1/chicago/ VALID_FOR=(ALL_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=chicago'LOG_ARCHIVE_DEST_2='SERVICE=boston VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=boston'

LOCATION and SERVICE AttributesEach LOG_ARCHIVE_DEST_n destination must specify either the LOCATION attribute or the SERVICE attribute to identify either a local disk directory or a remote database destination where log transport services can transmit redo data.LOCATION: Each destination that specifies the LOCATION attribute must identify a unique directory path name. This is the local destination for archived redo logs.SERVICE: Specifies a valid Oracle Net Services name. This service may be one of the following:

• A standby database (either physical logical)• An archive log repository, allowing for off-site archiving of redo logs. An archive log

repository is created by using a standby control file, starting the instance, and mounting the database. This destination contains no data files. Note: The Data Guard broker does not support this type of service.

• A cross-instance archival database environment is possible on both the primary and standby databases. In a RAC environment, each instance directs its archived redo logs to a single instance of the cluster. The recovery instance typically has a tape drive available for RMAN backup and restore support. Note: The Data Guard broker does not support this type of service.

Note: There are no defaults for these attributes.



LOG_ARCHIVE_DEST_STATE_n

• Defines the current state of an archive log destination:– ENABLE (default)– DEFER

– RESET

– ALTERNATE

• Applies to the primary and standby databaselog_archive_dest _3='SERVICE=stby1_path1 NOREOPEN ALTERNATE=LOG_ARCHIVE_DEST_4'log_archive_dest _4='SERVICE=stby1_path2 NOREOPEN'log_archive_dest_state_3=ENABLElog_archive_dest_state_4=ALTERNATE

LOG_ARCHIVE_DEST_STATE_n

The LOG_ARCHIVE_DEST_STATE_n initialization parameter (where n is an integer from 1 to 10) specifies the state of the corresponding destination that is indicated by the LOG_ARCHIVE_DEST_n initialization parameter (where n is the same integer). For example, the LOG_ARCHIVE_DEST_STATE_2 parameter specifies the state of the LOG_ARCHIVE_DEST_2 destination. The following are the valid values:• ENABLE: Specifies that a valid log archive destination can be used for a subsequent

archiving operation (automatic or manual). This is the default.• DEFER: Specifies that valid destination information and attributes are preserved but

that the destination is excluded from archiving operations until reenabled• RESET: Functions similarly to DEFER but clears any error messages for the

destination if it had previously failed• ALTERNATE: Specifies that the destination is not enabled but becomes enabled if

communication with another destination failsIn the example on the slide, destination 4 is an alternate for destination 3. Notice that destination 3 has a state of ENABLE and 4 has a state of ALTERNATE. This has the effect of making destination 4 wait for 3 to fail. In that case, the state of destination 4 becomes ENABLE and the state of destination 3 becomes DEFER.



Specifying Values for DB_FILE_NAME_CONVERT

• Must be defined on standby databases that have different disk or directory structures from the primary

• Allows multiple pairs of file names• Applies to a database when in physical standby

modeDB_FILE_NAME_CONVERT =('/oracle1/dba/',

'/ora1/stby_dba/','/oracle2/dba/','/ora2/stby_dba/')

Specifying Values for DB_FILE_NAME_CONVERTWhen the standby database is updated, the DB_FILE_NAME_CONVERT parameter is used to convert the data file name on the primary database to a data file name on the standby database. The file must exist and be writable on the physical standby database; if it is not, then the recovery process halts with an error.Specify the path name and file name location of the primary database data files followed by the standby location by setting the value of this parameter to two strings. The first string is the pattern found in the data file names on the primary database. The second string is the pattern found in the data file names on the physical standby database. You can use as many pairs of primary and standby replacement strings as required. You can use single or double quotation marks. The parentheses are optional. In the example in the slide, /oracle1/dba/ and /oracle2/dba/ are used to match for file names coming from the primary database. The strings /ora1/stby_dba/ and /ora2/stby_dba/ are the corresponding ones on the physical standby database. A file on the primary database named /oracle1/dba/system01.dbf is converted to /ora1/dba/system01.dbf on the standby database.



Specifying Values for LOG_FILE_NAME_CONVERT

• Similar to DB_FILE_NAME_CONVERT• Must be defined on standby databases that have

different disk or directory structures from the primary

• Online redo log files are used only when the standby becomes a primary.

• Applies to a database when in physical standby mode

LOG_FILE_NAME_CONVERT = ('/oracle1/logs/','/ora1/stby_logs/')

Specifying Values for LOG_FILE_NAME_CONVERTThe LOG_FILE_NAME_CONVERT parameter is used to convert the name of a redo log file on the primary database to the name of a redo log file on the standby database. Adding a redo log file to the primary database requires adding a corresponding file to the standby database. When the standby database is updated, this parameter is used to convert the log file name from the primary database to the log file name on the standby database. This parameter is required if the standby database is on the same system as the primary database or on a separate system that uses different path names.Specify the location of the primary database online redo log files followed by the standby location. The use of parentheses is optional.



Specifying a Value for LOG_ARCHIVE_FORMAT

• Indicates the format for redo log file names• Format directives:

– %t: Thread number– %T: Zero-filled thread number– %s: Sequence number– %S: Zero-filled sequence number– %d: Database ID– %D: Zero-filled database ID – %a: Current activation id– %A: Zero-filled activation ID– %r: Resetlogs ID

• Default value is operating system dependent.LOG_ARCHIVE_FORMAT = %d_%t_%s_%r.arc

Specifying a Value for LOG_ARCHIVE_FORMATUse a text string and variables to specify the default file name format for archived redo log files. The string that is generated from this format is appended to the string that is specified in the LOG_ARCHIVE_DEST_n and STANDBY_ARCHIVE_DEST parameters.The thread number refers to the redo thread. With a single instance, this is always 1; with RAC, this corresponds to the order in which the instances were started.Sequence number is the redo log sequence number. It starts at 0 or 1 and is incremented at each log switch.The database identifier (database ID) is calculated when the database is created and stored in all file headers. This value is not changed for the life of the database.The activation number is an internal number that is generated the first time the database is started. Subsequently, it is changed only when the database is opened with the RESETLOGSoption.The resetlogs ID ensures unique names are constructed for the archived log files across multiple incarnations of the database. If the COMPATIBLE initialization parameter is set to 10.0 or higher, you must include %r in the LOG_ARCHIVE_FORMAT parameter. The length of the zero-filled versions of these directives is 8 on most platforms.



Specifying a Value for STANDBY_FILE_MANAGEMENT

• Used to maintain consistency when you add or delete a data file on the primary database– MANUAL (default)

Data files must be manually added on the standby database.

– AUTO

Add the data file automatically to the standby database.Certain ALTER statements are no longer allowed on the standby database.

• Applies to the primary database and standby database

STANDBY_FILE_MANAGEMENT = auto

Specifying a Value for STANDBY_FILE_MANAGEMENTWhen STANDBY_FILE_MANAGEMENT is set to AUTO, you cannot execute the following commands on the standby database:• ALTER DATABASE RENAME• ALTER DATABASE ADD/DROP LOGFILE [MEMBER]• ALTER DATABASE ADD/DROP STANDBY LOGFILE MEMBER• ALTER DATABASE CREATE DATAFILE AS ...

When you add (or drop) a log file to the primary and want to add (or drop) it to the standby as well, you must do the following:

• Set STANDBY_FILE_MANAGEMENT to MANUAL on the standby.• Add (or drop) the redo log files on the primary.• Add (or drop) them to the standbys.• Reset to AUTO afterward on the standby.



ARCHIVE_LAG_TARGET

• Configure on primary database only• Set to the number of seconds after which a log

switch must happen even if the log file is not full• Sets maximum time that a standby database must

wait to process the redo• Default is 0 (disabled)• Range of values: 60 to 7,200• Recommended value: 1,800 (30 minutes)

ARCHIVE_LAG_TARGET = 1800

ARCHIVE_LAG_TARGET

The ARCHIVE_LAG_TARGET parameter defines the mean time to failover in the event your primary database fails and you must fail over to the standby. Although the redo is transmitted to the standby during normal operations, it is not applied to the standby database until the online redo log file on the primary has been completed.For example, in a configuration where the online redo log file is 100 MB and 80 MB have been written, a failure at this point would mean that the 80 MB of redo must be applied to the standby before the failover can complete. If you need to limit the amount of time to get the standby up and running as a primary after a failover, you can define this parameter to force a log switch after a certain amount of time, thereby enabling the redo to be applied.If you set this parameter to too small a value, the primary database log files switch too often and thus impact performance.



LOG_ARCHIVE_TRACE Parameter

• LOG_ARCHIVE_TRACE is optional and is used for diagnostic purposes.

• Set this parameter to an integer value to see the progression of the archiving of redo logs to the standby system.– On the primary, processes write an audit trail of the

archived logs sent to the standby system into a trace file.

– On the standby, processes write an audit trail of the archived logs received from the primary database into a trace file.

• Trace files are located in the directory specified by the USER_DUMP_DEST parameter.

LOG_ARCHIVE_TRACE ParameterYou can set this parameter to trace the transmission of redo data to the standby system. To enable, disable, or modify the LOG_ARCHIVE_TRACE parameter in a primary database, do one of the following:

• Shut down the primary database, modify the initialization parameter file, and restart the database.

• Issue an ALTER SYSTEM SET LOG_ARCHIVE_TRACE=trace_levelstatement while the database is open or mounted.

If you change the value of this parameter dynamically with an ALTER SYSTEM statement, the changes take effect at the start of the next archive operation.Refer to Oracle Data Guard Concepts and Administration for additional information.


LOG_ARCHIVE_TRACE Parameter (continued)The integer values for the LOG_ARCHIVE_TRACE parameter represent levels of tracing data. In general, the higher the level, the more detailed the information. You can combine tracing levels by setting the value of the LOG_ARCHIVE_TRACE parameter to the sum of the individual levels. For example, setting the parameter to 6 generates level 2 and level 4 trace output.The following integer levels are available:

Level Meaning 0 Disables archived redo log tracing (default setting) 1 Tracks archiving of redo log file 2 Tracks archival status per archived redo log destination 4 Tracks archival operational phase 8 Tracks archived redo log destination activity 16 Tracks detailed archived redo log destination activity 32 Tracks archived redo log destination parameter modifications 64 Tracks ARCn process state activity 128 Tracks FAL server process activity 256 Reserved for future use 512 Tracks asynchronous LGWR activity 1024 Tracks RFS physical client 2048 Tracks ARCn or RFS heartbeat 4096 Tracks real-time apply activity



Backing Up the Primary Database by Using RMAN

RMAN> BACKUP DATABASE

• Create a backup copy of the primary database.• Use of RMAN is recommended.

Backing Up the Primary Database by Using RMANYou can use any backup copy of the primary database to create the physical standby database, as long as you have the necessary archived redo log files to completely recover the database. It is recommended that you use Recovery Manager (RMAN).See Oracle High Availability Architecture and Best Practices for backup recommendations and Oracle Database Backup and Recovery Advanced User’s Guide for additional information about performing the RMAN backup operation.



Creating a Control File for the Standby Database

SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE 2 AS '/tmp/boston.ctl';

Create a control file on the primary database to be used for the standby database:

Creating a Control File for the Standby DatabaseOn the primary database, you create the control file for the standby database. Create the control file by issuing the following command:

ALTER DATABASE CREATE STANDBY CONTROLFILE AS file_name [REUSE];

If the file already exists, you can use the REUSE option to overwrite it.Note: You cannot use a single control file for both the primary and standby databases.



Copying Files to the Standby Database System

Copy the following files to the standby database system:• Backup of the data files• Standby control file• Initialization parameter file

Primary Standby

Copying Files to the Standby Database SystemAfter you have successfully backed up the data files and created the standby database control file, copy the files to the standby system by using an operating system utility. If the physical standby database is on a different system from the primary database, then the directory paths may be the same. If the physical standby database is on the same system as the primary database, you must rename the primary data files in the standby control file after copying them to the standby location.



Oracle Managed Files (OMF) and Automatic Storage Management (ASM)

• OMF: Use same on each database• ASM: Use the RMAN DUPLICATE … FOR STANDBY

command

OMF primary

OMF standby

Oracle Managed Files (OMF) and Automatic Storage Management (ASM)If the primary database is configured to use OMF, Oracle recommends that the standby database be configured to use OMF as well. To do this, set the DB_CREATE_FILE_DESTand DB_CREATE_ONLINE_LOG_DEST_n initialization parameters to appropriate values. Maintenance and future role transitions are simplified if the same disk group names are used for both the primary and standby databases.On the standby database, do the following:

1. If the standby database is going to use ASM, create an ASM instance if one does not already exist on the standby database system.

2. Use the RMAN BACKUP command to create a backup set that contains a copy of the primary database’s data files, archived log files, and a standby control file.

3. Use the RMAN DUPLICATE … FOR STANDBY command to copy the data files, archived redo log files, and standby control file in the backup set to the standby database’s storage area. The DUPLICATE … FOR STANDBY command performs the actual data movement at the standby instance.

For more information about OMF and ASM, see the Oracle Database Administrator's Guide. For more information about the DUPLICATE … FOR STANDBY command, see the Oracle Database Recovery Manager Reference.



Initialization Parameters on the Standby

DB_NAME=chicagoDB_UNIQUE_NAME=bostonSERVICE_NAMES=bostonLOG_ARCHIVE_CONFIG='DG_CONFIG=(chicago,boston)'CONTROL_FILES='/arch1/boston/control1.ctl', '/arch2/boston/control2.ctl'DB_FILE_NAME_CONVERT= '/arch1/chicago/','/arch1/boston/', '/arch2/chicago/','/arch2/boston/'LOG_FILE_NAME_CONVERT='/arch1/chicago/','/arch1/boston/', '/arch2/chicago/','/arch2/boston/'LOG_ARCHIVE_FORMAT=log%t_%s_%r.arcLOG_ARCHIVE_DEST_1= 'LOCATION=/arch1/boston/ VALID_FOR=(ALL_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=boston'LOG_ARCHIVE_DEST_2= 'SERVICE=chicago VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=chicago'LOG_ARCHIVE_DEST_STATE_1=ENABLELOG_ARCHIVE_DEST_STATE_2=ENABLEREMOTE_LOGIN_PASSWORDFILE=EXCLUSIVESTANDBY_FILE_MANAGEMENT=AUTOINSTANCE_NAME=bostonFAL_SERVER=chicagoFAL_CLIENT=boston

Initialization Parameters on the StandbyCreate a text initialization parameter file (PFILE) from the server parameter file (SPFILE) that is used by the primary database. A PFILE can be copied to the standby location and modified. Issue the following command to create the PFILE:

SQL> CREATE PFILE='/tmp/initboston.ora' FROM SPFILE;

Later, you will convert this file back to a SPFILE after it is modified to contain the parameter values that are appropriate for use with the physical standby database.Although most of the initialization parameter settings in the text initialization parameter file that you copied from the primary system are also appropriate for the physical standby database, some modifications need to be made. The lines in italic in the slide indicate the parameters that need to be changed for use with the physical standby. The parameters shown are valid for the Boston database when it is running in either the primary or the standby database role.In addition, ensure that the COMPATIBLE initialization parameter is set to the same value on both the primary and standby databases. If the values differ, log transport services may be unable to transmit redo data from the primary database to the standby databases. In a Data Guard configuration, COMPATIBLE must be set to a minimum of 9.2.0.1.0. However, if you want to take advantage of new Oracle Database 10g features, set the COMPATIBLEparameter to 10.1.0.0 or higher.



Specifying a Value for STANDBY_ARCHIVE_DEST

• Defines the standby database directory where the archived redo log files are created

• Overrides the directory location that is specified with the LOG_ARCHIVE_DEST_n parameter

STANDBY_ARCHIVE_DEST = '/standby/arc_dest/'

STANDBY_ARCHIVE_DEST = 'LOCATION=/standby/arc_dest/'

Specifying a Value for STANDBY_ARCHIVE_DESTYou can use the STANDBY_ARCHIVE_DEST initialization parameter on the standby database to indicate an alternative directory where the archived redo log files are to be stored when received from the primary database.The STANDBY_ARCHIVE_DEST initialization parameter overrides the directory location that is specified with the LOG_ARCHIVE_DEST_n parameter if both parameters are specified.You should set STANDBY_ARCHIVE_DEST to the same location as the local archive destination for the physical standby database so that all necessary archived redo log files for the standby database are in the same location.Because logical standbys have at least one local archive destination, STANDBY_ARCHIVE_DEST is not set in most configurations.STANDBY_ARCHIVE_DEST and LOG_ARCHIVE_FORMAT are used to construct a fully qualified file name.



Setting Up the Environment to Support the Standby Database

1. Create a Windows-based service.2. Create a password file.3. Configure listeners for the primary and standby

databases.

Setting Up the Environment to Support the Standby Database1. If the standby system is running on a Windows-based system, use the ORADIM tool to

create a Windows service and password file. Here is an example:WINNT> oradim -NEW -SID boston -INTPWD password -STARTMODE manual

See Oracle Database Platform Guide for Windows for more information about using the ORADIM tool.

2. On platforms other than Windows, create a password file and set the password for the SYS user to the same password that is used by the SYS user on the primary database. The password for the SYS user on every database in a Data Guard configuration must be identical for redo transmission to succeed. See Oracle Database Administrator’s Guide for information about creating a password file.

3. On both the primary and standby sites, use Oracle Net Manager to configure a listener for the respective databases. To restart the listeners so that they recognize the new definitions, enter the following Listener Control utility commands on both the primary and standby systems:

% lsnrctl stop% lsnrctl start

See Oracle Net Services Administrator’s Guide for additional information about the Listener Control utility.



Setting Up the Environment to Support the Standby Database

4. Enable broken connection detection on the standby system.

5. Create Oracle Net Services names.6. Create a server parameter file for the standby

database.

Setting Up the Environment to Support the Standby Database (continued)4. Enable broken connection detection by setting the SQLNET.EXPIRE_TIME

parameter to 2 (minutes) in the SQLNET.ORA parameter file on the standby system. Here is an example:

SQLNET.EXPIRE_TIME=2

See the Oracle Net Services Administrator’s Guide for additional information.5. On both the primary and standby systems, use Oracle Net Manager to create a network

service name for the primary and standby databases that will be used by log transport services. The Oracle Net Services name must resolve to a connect descriptor that uses the same protocol, host address, port, and SID that you specified when you configured the listeners for the primary and standby databases. The connect descriptor must also specify that a dedicated server be used. See the Oracle Net Services Administrator’s Guide and the Oracle Database Administrator’s Guide.

6. On an idle standby database, use the CREATE SPFILE SQL statement to create a server parameter file for the standby database from the text initialization parameter file that was edited earlier, as shown in the following example:

SQL> CREATE SPFILE FROM PFILE='initboston.ora';



Starting Up the Physical Standby Database

To start up the physical standby database:1. Bring it to the OPEN READ ONLY stage.2. Create a new temporary file for the physical

standby database.3. Start Redo Apply.4. Test archival operations to the physical standby

database:SQL> STARTUP;

SQL> ALTER TABLESPACE TEMP1 ADD TEMPFILE

2 '/boston/temp01.dbf' SIZE 40M REUSE;

SQL> ALTER DATABASE RECOVER MANAGED STANDBY

2 DATABASE DISCONNECT FROM SESSION;

Starting Up the Physical Standby Database1. On the standby database, issue the STARTUP SQL statement to start the instance and

open the database in read-only mode.2. It is beneficial to create a new temporary file on the physical standby database now

rather than later. Temporary files enable disk sorting when the database is open in read-only mode and prepare the database for future role transitions. Identify the tablespaces that should contain temporary files by entering the following command on the standby database:

SQL> SELECT TABLESPACE_NAME FROM DBA_TABLESPACES2 WHERE CONTENTS = 'TEMPORARY';

3. On the standby database, issue the ALTER DATABASE RECOVER MANAGED STANDBY DATABASE SQL command to start Redo Apply. This statement automatically mounts the database. Also, include the DISCONNECT FROM SESSIONoption so that Redo Apply runs in a background session.

4. The transmission of redo data to the remote standby location does not occur until after a log switch. Issue the following command on the primary to force a log switch:

SQL> ALTER SYSTEM SWITCH LOGFILE;



Additional Configuration Tasks

Perform the following tasks as appropriate for your configuration:• Configure standby redo logs.• Enable Flashback Database.• Upgrade the data protection mode.

Additional Configuration TasksPerform the following tasks if they are appropriate for your physical standby database:

• Configure standby redo logs: Standby redo logs are required for standby databases running in the maximum protection mode and maximum availability mode. However, configuring standby redo logs is recommended on all standby databases because, during a failover, Data Guard can recover and apply more redo data from standby redo log files than from the archived redo log files alone. The standby redo logs should exist on both primary and standby databases and have the same size and names.

• Enable Flashback Database: Flashback Database removes the need to re-create the primary database after a failover. Flashback Database is similar to conventional point-in-time recovery in its effects, enabling you to return a database to a recent past state. Flashback Database is faster than point-in-time recovery because it does not require restoring data files from backup or the extensive application of redo data. You can enable Flashback Database on the primary database, the standby database, or both.

• Upgrade the data protection mode: The Data Guard configuration is initially set up in the maximum performance mode (the default).



Special Note:Standby Database on Same System

• Standby database data files must be in a different location.

• Each database instance must archive to different locations.

• Service names must be unique.• The standby database does not protect against

disaster.

Primary Standby /oracle/dba /oracle/standby/dba

Special Note: Standby Database on Same SystemIf you have a standby database on the same system as the primary database, you must consider the following:

• The data files must be renamed. The actual file names can be the same, but at least the directory path must be different. This means that you must use the DB_FILE_NAME_CONVERT and LOG_FILE_NAME_CONVERT parameters.

• If a standby database is located on the same system as the primary database, the archival directories for the standby database must use a different directory structure than the primary database. Otherwise, the standby database may overwrite the primary database files.

• If you do not explicitly specify unique service names and if the primary and standby databases are located on the same system, the same default global name (consisting of the database name and domain name, from the DB_NAME and DB_DOMAINparameters) will be in effect for both databases.

• If the standby database is on the same system as the primary database, it does not protect against disaster. A disaster is defined as a total loss of the primary database system. If the standby database is on the same system, it will be lost as well. This configuration should be used for testing and training purposes only.



Summary

In this lesson, you should have learned how to:• Create a physical standby with SQL commands• Enable FORCE LOGGING• Back up the primary database• Copy files to the standby system• Set parameters on the physical standby database• Start the standby database• Configure Oracle Net Services• Set parameters on the primary database• Start the transport of redo


Data Protection Modesand Log Transport Services



Objectives

After completing this lesson, you should be able to do the following:• Describe the data protection modes• Change the data protection mode of your

configuration• Modify log transport services to serve your needs



Data Protection Modes and Log Transport Modes

• A data protection mode requires a specific log transport mode.

• A log transport mode alone does not define a data protection mode.

Data Protection Modes and Log Transport Modes When you define a log transport mode, you are configuring the shipment of log files from the primary database to the standby database (physical or logical). You must set your log transport mode to support the protection mode that you want for your configuration. However, configuring the log transport mode alone does not set up the protection mode.After you set up the log transport mode, you can put the configuration into the desired data protection mode. The data protection mode setting causes internal rules to be implemented, ensuring that your configuration is protected at the level you desire.



Attributes of LOG_ARCHIVE_DEST_n

• ARCH and LGWR– Specify that either the archiver process or the log

writer process is responsible for transmitting redo to the standby destination

– ARCH is the default.• SYNC and ASYNC

– Specify that network I/O operations are to be performed synchronously or asynchronously when using the log writer process

– SYNC is the default and also has a parallel option.• AFFIRM and NOAFFIRM

– Ensure that redo has been successfully written to disk on the standby destination

– NOAFFIRM is the default.

Attributes of LOG_ARCHIVE_DEST_nThe following attributes of the LOG_ARCHIVE_DEST_n initialization parameter define the log transport mode that is used by the primary database to send redo to the standby database:• ARCH: Indicates that redo logs are transmitted to the destination during an archival

operation. A foreground archival operation or the archiver background processes (ARCn) serve as the redo log transport service. This is the default.

• LGWR: Indicates that redo is transmitted to the destination concurrently while the online redo log is being written. The log writer background process (LGWR) serves as the redo log transport service. When transmitting redo to remote destinations, the LGWR process establishes a network connection to the destination instance. If a LGWR destination fails, the destination automatically reverts to using the archiver process until the error is corrected. With the LGWR attribute, you have the following additional options:

- SYNC=PARALLEL|NOPARALLEL: Specifies that network I/O is to be performed synchronously for the destination. This means that after the I/O is initiated, the LGWR process waits for the I/O to complete before


Attributes of LOG_ARCHIVE_DEST_n (continued)continuing. The SYNC attribute is required when setting up a no-data-loss environment because it ensures that the redo records have been successfully transmitted to the standby database before continuing.If the LGWR process is defined to be the transmitter to multiple standby destinations that use the SYNC attribute, the user has the option of specifying SYNC=PARALLEL or SYNC=NOPARALLEL for each of those destinations. If SYNC=NOPARALLEL is used, LGWR performs the network I/O to each destination serially. In other words, LGWR initiates an I/O to the first destination and waits until it completes before initiating the I/O to the next destination. If SYNC=PARALLEL is used, the network I/O is actually initiated asynchronously so that I/O to multiple destinations can be initiated in parallel. However, after the I/O is initiated, the LGWR process waits for each of the I/O operations to complete before continuing, which in effect is the same as performing multiple, synchronous I/O operations simultaneously. The use of SYNC=PARALLELresults in better performance than SYNC=NOPARALLEL when multiple LGWR SYNC destinations are configured. SYNC=PARALLEL is the default.

- ASYNC[=blocks]: Specifies that network I/O is to be performed asynchronously for the destination. This means that after the I/O is initiated, LGWR continues processing the next request without waiting for the I/O to complete and without checking the completion status of the I/O. Use of the ASYNC attribute allows standby environments to be maintained with little or no performance impact on the primary database. The optional block count determines the size of the SGA network buffer to be used. In general, the slower the network connection, the larger the block count. The default is 2048.

• AFFIRM: Ensures that all disk I/O to the archived redo log files or standby redo log files at the standby destination is performed synchronously and completes successfully before online redo log files on the primary database can be reused. This attribute has the potential to affect primary database performance. When you use the LGWR, SYNC, and AFFIRM attributes, the transaction is not committed until the disk I/O is completed.

• NOAFFIRM: Indicates that all redo disk I/O operations are to be performed asynchronously, which means that the log writer process does not wait until the disk I/O has completed before continuing. This is the default.



Setting the Log Transport Mode

Click Edit to access the Edit Standby Database Properties

page.

Setting the Log Transport ModeUse the following procedure to set the log transport mode with Enterprise Manager:

1. Select your standby database, and then click Edit on the Data Guard page.2. Click “Standby Role Properties” on the Edit Standby Database Properties page.3. Click “Show Advanced Properties.”



Setting the Log Transport Mode

Select the mode from the Log Transport

Mode list.

Setting the Log Transport Mode (continued)You can use the drop-down list to select the log transport mode on the Standby Role Properties page. The values in the Log Transport Mode list are defined as follows: • ARCH: Configures log transport services for your standby database using the ARCH

attribute of the LOG_ARCHIVE_DEST_n initialization parameter. You do not need standby redo log files for this mode. This mode enables the lowest grade of protection to the primary database as well as the lowest performance impact.

• ASYNC: Configures log transport services for your standby database using the LGWR, ASYNC, and NOAFFIRM attributes of the LOG_ARCHIVE_DEST_n initialization parameter. This mode, along with standby redo log files, enables a moderate grade of protection to the primary database and incurs a lower performance impact.

• SYNC: Configures log transport services for your standby database using the LGWR, SYNC, and AFFIRM attributes of the LOG_ARCHIVE_DEST_n initialization parameter. This mode, along with standby redo log files, is required for the maximum protection or maximum availability protection modes. This log transport mode enables the highest grade of data protection to the primary database, but it also incurs the highest performance impact.



Data Protection Modes

• Three data protection modes:– Maximum protection– Maximum availability– Maximum performance

• Help to balance data availability and system performance

Data Protection ModesOracle Data Guard offers maximum protection, maximum availability, and maximum performance modes to help enterprises balance data availability against system performance requirements.In some situations, a business cannot afford to lose data. In other situations, the availability of the database may be more important than the loss of data. Some applications require maximum database performance and can tolerate a potential loss of data.



Maximum Protection

• Enables zero data loss• Redo data must be written to both the local online

redo log and the standby redo log on at least one standby database.

• Primary database shuts down if a fault prevents it from writing its redo stream to at least one remote standby redo log.

• Configuration requirements:– Standby redo log files on at least one standby

database– SYNC, LGWR, and AFFIRM attributes

for at least one standby database

Maximum ProtectionThis protection mode ensures that no data loss will occur if the primary database fails. To provide this level of protection, the redo data needed to recover each transaction must be written to both the local online redo log and the standby redo log on at least one standby database before the transaction commits. To ensure that data loss cannot occur, the primary database shuts down if a fault prevents it from writing its redo stream to at least one remote standby redo log. For multiple-instance RAC databases, Data Guard shuts down the primary database if it is unable to write the redo records to at least one properly configured database instance. To enable maximum protection mode, perform the following configuration tasks:

• Configure standby redo log files on at least one standby database. • Set the SYNC, LGWR, and AFFIRM attributes of the LOG_ARCHIVE_DEST_n

parameter for at least one standby database destination.



Maximum Availability

• Provides the highest possible level of data protection without compromising the availability of the primary database

• Redo data must be written to both the local online redo log and the standby redo log on at least one standby database.

• Primary database does not shut down if a fault prevents it from writing its redo stream.

• Configuration requirements:– Standby redo log files on at least one standby

database– SYNC, LGWR, and AFFIRM attributes

for at least one standby database

Maximum AvailabilityThis protection mode provides the highest possible level of data protection without compromising the availability of the primary database. Like maximum protection mode, a transaction will not commit until the redo needed to recover that transaction is written to the local online redo log and to at least one remote standby redo log. Unlike maximum protection mode, the primary database does not shut down if a fault prevents it from writing its redo stream to a remote standby redo log. Instead, the primary database operates in maximum performance mode until the fault is corrected and all gaps in redo log files are resolved. When all gaps are resolved, the primary database automatically resumes operating in maximum availability mode.This mode guarantees that no data loss will occur if the primary database fails, but only if a second fault does not prevent a complete set of redo data from being sent from the primary database to at least one standby database.To enable maximum availability mode, perform the following configuration tasks:

• Configure standby redo log files on at least one standby database. • Set the SYNC, LGWR, and AFFIRM attributes of the LOG_ARCHIVE_DEST_n

parameter for at least one standby database.



Maximum Performance

• Default level of data protection• Provides highest possible level of data protection

without affecting the performance of the primary database

• Transaction can commit as soon as the redo data is written to the local online redo log.

• Redo stream is written asynchronously with respect to the commitment of the transactions that create the redo data.

Maximum PerformanceThis protection mode (the default) provides the highest possible level of data protection without affecting the performance of the primary database. This is accomplished by allowing a transaction to commit as soon as the redo data needed to recover that transaction is written to the local online redo log. The primary database's redo data stream is also written to at least one standby database, but that redo stream is written asynchronously with respect to the commitment of the transactions that create the redo data.When network links with sufficient bandwidth are used, this mode provides a level of data protection that approaches that of maximum availability mode with minimal impact on primary database performance.The maximum performance mode enables you to either set the LGWR and ASYNC attributes or set the ARCH attribute on the LOG_ARCHIVE_DEST_n parameter for the standby database destination. If the primary database fails, you can reduce the amount of data that is not received on the standby destination by setting the LGWR and ASYNC attributes.



Setting the Data Protection Mode

Click the Protection Mode link.

Setting the Data Protection ModeIf the data protection mode that you need requires a standby database to use the SYNC or ASYNC log transport mode, Enterprise Manager will automatically set the log transport mode for the primary database and the selected standby databases.Enterprise Manager automatically determines the correct number and size of standby redo log files needed for all databases in the configuration and adds those log files using the directory locations you specify.After you upgrade the protection mode using Enterprise Manager, the primary database will be restarted automatically. The primary database need not be restarted following a downgrade of the protection mode.You can set the data protection mode by using Enterprise Manager as follows:

1. Navigate to the Data Guard page.2. Click the link in the Protection Mode field to access the Edit Protection Mode: Select

page.



Setting the Data Protection Mode

Setting the Data Protection Mode (continued)3. Select Maximum Protection, Maximum Availability, or Maximum Performance, and

then click Continue.4. If prompted, log in to the database with SYSDBA privileges, and then click Login.5. Select one or more standby databases to support the protection mode that you selected.

If standby redo log files are needed, verify the names of the log files. Click OK.6. On the Confirmation page, click Yes.



Setting the Data Protection Mode by Using the CLI

1. Configure standby redo logs.2. Set the LogXptMode property (if necessary).3. Set the data protection mode.DGMGRL> EDIT DATABASE 'site1_edrsr8p1' SET PROPERTY 'LogXptMode'='SYNC';DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;

Setting the Data Protection Mode by Using the CLI1. If you are setting the protection mode to maximum protection or maximum

availability, ensure that standby redo log files are configured on the standby database. You must also configure standby redo log files for the primary database or another standby database in the configuration to ensure that it can support the chosen protection mode after a switchover.

2. Use the EDIT DATABASE SET PROPERTY command to set the log transport mode for the standby database. For example, if you are changing the data protection mode to maximum availability, use the EDIT DATABASE command to specify SYNC for log transport services as follows:DGMGRL> EDIT DATABASE 'DR_Sales' SET PROPERTY 'LogXptMode'='SYNC';

You must also set the log transport services for the primary database or another standby database in the configuration to ensure that it can support the chosen protection mode after a switchover.

3. Use the EDIT CONFIGURATION SET PROTECTION MODE AS command to set the overall configuration protection mode. To set the protection mode to maximum availability, issue the following command:DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;



Setting the Protection Mode by Using SQL

• You must set attributes to support the type of protection desired.

• Issue the ALTER DATABASE statement on the primary database:

ALTER DATABASE SET STANDBY TO MAXIMIZE PROTECTION;

Setting the Protection Mode by Using SQLYou must set attributes of the LOG_ARCHIVE_DEST_n initialization parameter for each level of protection. For each level of protection, you must have at least one standby database with the following:

• Maximum protection: LGWR, SYNC, AFFIRM, and standby redo logs files• Maximum availability: LGWR, SYNC, AFFIRM, and standby redo logs files for

physical standby databases• Maximum performance: any combination of LGWR or ARCH

Using the following SQL statement on the primary database, you can configure the Data Guard environment to maximize data protection, availability, or performance:ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE {PROTECTION | AVAILABILITY | PERFORMANCE};



Delaying the Application of Redo

Delaying the application of redo helps to safeguard against:• Data corruption• User errors

Productiondatabase

Standbydatabase

Ora

cle

Net Delayed

application

Delaying the Application of RedoYou can delay the application of changes to standby databases, thereby providing protection from user errors or corruptions. You can protect against the application of corrupted or erroneous data to the standby database. The apply process also revalidates the log records to prevent application of log corruptions.For example, if a critical table is accidentally dropped from the primary database, you can prevent this action from affecting the standby database by delaying the application of this change in the standby database.If operating in maximum protection or maximum availability mode, Data Guard will ensure zero data loss even with the delayed apply in effect.If you define a delay for a destination that has real-time apply enabled, the delay is ignored.



Using Enterprise Manager to Delay the Application of Redo

Specify the delay in minutes.

Using Enterprise Manager to Delay the Application of RedoYou can configure delayed apply by using Enterprise Manager as follows:

1. On the Data Guard page, select your standby database. Then click Edit.2. On the Edit Standby Database Properties page, click Standby Role Properties.3. Click the Show Advanced Properties link.4. In the Apply Delay field, enter the delay value (in minutes). 5. Click Apply.



Setting LOG_ARCHIVE_DEST_nto Delay the Application of Redo

Use the attributes of LOG_ARCHIVE_DEST_n to control the application of redo:• DELAY: Number of minutes to delay application of

redo (default: 30 minutes)• NODELAY: Redo applied as received (default

behavior)

Setting LOG_ARCHIVE_DEST_n to Delay the Application of RedoYou can use the DELAY=minutes attribute of the LOG_ARCHIVE_DEST_n initialization parameter to delay the application of archived redo log files to the standby database on the primary database and physical standby databases.Note: If you do not specify a value for minutes, the default is 30 minutes.



Using Flashback Database Instead of Apply Delay

No delay

4-hour delay

Standby1

Standby2

Standby3

8-hour delay

Standby

Primary database

Primary database

Using Flashback Database Instead of Apply DelayAs an alternative to the Apply Delay configuration option, you can use Flashback Database to protect against the application of corrupted or erroneous data to the standby database. Flashback Database can quickly and easily flash back a standby database to an arbitrary time in the past. You can configure one standby database with Flashback Database to achieve the same benefit as multiple standby databases with different delays.Refer to the Oracle Database Backup and Recovery Advanced User’s Guide for additional information on Flashback Database.



Additional Attributes That Affect Log Transport Services

• ALTERNATE, NOALTERNATE

• DEPENDENCY, NODEPENDENCY

• MAX_FAILURE, NOMAX_FAILURE

• NET_TIMEOUT, NONET_TIMEOUT

• REOPEN, NOREOPEN

Additional Attributes That Affect Log Transport ServicesThe following pages present additional attributes of the LOG_ARCHIVE_DEST_ninitialization parameter that affect log transport services. The use of each attribute depends entirely on your individual business requirements.



ALTERNATE and NOALTERNATE Attributes

• Can specify one alternate destination for the LOG_ARCHIVE_DEST_n parameter

• Allow a failed destination to change destinations– Disk full: switch to new disk– Oracle Net link fails: switch to new network link

• Require NOREOPEN or MAX_FAILURE• Enabled with LOG_ARCHIVE_DEST_STATE_n• Default: NOALTERNATElog_archive_dest_3='SERVICE=stby1_path1 NOREOPEN ALTERNATE=LOG_ARCHIVE_DEST_4'log_archive_dest_4='SERVICE=stby1_path2 NOREOPEN OPTIONAL'log_archive_dest_state_3=ENABLElog_archive_dest_state_4=ALTERNATE

ALTERNATE and NOALTERNATE AttributesYou can use the ALTERNATE attribute to specify another LOG_ARCHIVE_DEST_ndestination to be used if archival operations to the original destination fail. A destination can have a maximum of one alternate destination specified. An alternate destination is used when the transmission of redo fails. If the archiving to the destination fails and the REOPENattribute is specified with a value of zero (0), or if NOREOPEN is specified, the Oracle database server attempts to transmit the redo to the alternate destination on the next log switch.An alternate destination cannot be self-referencing.An alternate destination must be in the ALTERNATE state; this state is specified using the LOG_ARCHIVE_DEST_STATE_n initialization parameter. The ALTERNATE state defers processing of the destination until another destination failure automatically enables this destination (provided that the alternate destination attributes are valid).



MAX_FAILURE andNOMAX_FAILURE Attributes

MAX_FAILURE[=count]

• Number of times log transport services attempts to reestablish communication

• Requires REOPEN• No default countNOMAX_FAILURE

• Default• Same as MAX_FAILURE=0log_archive_dest_3='SERVICE=o10g1 LGWR MAX_FAILURE=30 REOPEN'

MAX_FAILURE and NOMAX_FAILURE AttributesThe MAX_FAILURE attribute of the LOG_ARCHIVE_DEST_n initialization parameter specifies the maximum number of consecutive times that log transport services reattempts archival operations to a failed destination. Using this attribute, you can provide failure resolution for archiving destinations to which you want to retry archival operations after a failure, but not retry indefinitely. When you specify the MAX_FAILURE attribute, you must also set the REOPEN attribute to specify how often archival operations are retried to the particular destination.If you set both the MAX_FAILURE and REOPEN attributes to nonzero values, log transport services limit the number of archival attempts to the number of times specified by the MAX_FAILURE attribute. Each destination contains an internal failure counter that tracks the number of consecutive archival failures that have occurred. You can view the failure count in the FAILURE_COUNT column of the V$ARCHIVE_DEST fixed view. The related column REOPEN_SECS identifies the REOPEN attribute value.



NET_TIMEOUT andNONET_TIMEOUT Attributes

• Enable the LGWR process to avoid a network timeout issue

• Valid with SYNC=PARALLEL or ASYNC destinations• Value supplied is the number of seconds to wait.• Range of values for NET_TIMEOUT: 15 to 1200• Default: NONET_TIMEOUT• Use caution in maximum protection mode

log_archive_dest_2='SERVICE=o10g2 LGWR SYNC=PARALLEL NET_TIMEOUT=30'

NET_TIMEOUT and NONET_TIMEOUT AttributesThe NET_TIMEOUT attribute enables you to bypass the default network timeout interval established for the system on which the primary database resides. Without the NET_TIMEOUT attribute (or if NONET_TIMEOUT is explicitly specified), the primary database can potentially stall for the default network timeout period. By specifying a smaller, nonzero value for NET_TIMEOUT, you can enable the primary database to mark a destination as “failed” after the user-specified timeout interval expires.Note: Be careful to specify a reasonable value when running in maximum protection mode. False network failure detection may cause the primary instance to shut down.



REOPEN and NOREOPEN Attributes

• REOPEN[=seconds]

– Minimum number of seconds to wait before retrying a failed destination at log switch

– Failures can be network failures, quota exceptions, disk full, and so on.

– Default: REOPEN with 300 seconds (5 minutes)• NOREOPEN

– Failed destinations remain disabled until:Manually reenabledALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_n=ENABLE issuedInstance restart

– Required when using ALTERNATE destinations with NOMAX_FAILURE attributes

REOPEN and NOREOPEN AttributesThe REOPEN and NOREOPEN attributes of the LOG_ARCHIVE_DEST_n parameter specify the minimum number of seconds before the process shipping the redo should try again to access a previously failed destination. REOPEN applies to all errors, not just connection failures. These errors include (but are not limited to) network failures, disk errors, and quota exceptions.



Summary

In this lesson, you should have learned how to:• Describe the data protection modes• Change the data protection mode of your

configuration• Modify log transport services to suit your needs• Delay the application of redo• Use additional transport services attributes




This practice covers the following topics:• Changing the data protection mode• Delaying the application of redo


Data Guard SQL Apply Architecture



Objectives

After completing this lesson, you should be able to do the following:• Explain the advantages of SQL Apply • Explain when to use a logical standby database• Create a logical standby database by using

Enterprise Manager



Benefits of Implementing aLogical Standby Database

• Provides an efficient use of system resources:– Open, independent, and active production database– Additional indexes and materialized views can be

created for improved query performance.• Reduces workload on the primary database by

offloading the following workloads to a logical standby database– Reporting– Summations– Queries

Benefits of Implementing a Logical Standby DatabaseA logical standby database provides disaster recovery, high availability, and data protection benefits that are similar to those of a physical standby database. It also provides the following specialized benefits:

• Efficient utilization of system resources: A logical standby database is an open, independent, and active production database. It can host multiple database schemas, and users can perform normal data manipulation operations on tables in schemas that are not updated from the primary database. It remains open while the tables are updated from the primary database, and those tables are simultaneously available for read-access. Because the data can be presented with a different physical layout, additional indexes and materialized views can be created to improve your reporting and query requirements and to suit your specific business requirements.

• Reduction in primary database workload: The logical standby tables that are updated from the primary database can be used for other tasks (such as reporting, summations, and queries), thereby reducing the primary database workload.



Benefits of Implementing aLogical Standby Database

• Provides data protection: – Primary database corruptions not propagated

• Provides disaster recovery capabilities:– Switchover and failover– Minimizes down time for planned and unplanned

outages

Benefits of Implementing a Logical Standby Database (continued)• Data protection: A logical standby database provides a safeguard against data

corruptions and user errors. Primary-side physical corruptions do not propagate through the redo data that are transported to the logical standby database. Similarly, user errors that may cause the primary database to be permanently damaged can be resolved before application on the logical standby through delay features.

• Disaster recovery: A logical standby database provides a robust and efficient disaster recovery solution. Easy-to-manage switchover and failover capabilities allow easy role reversals between primary and logical standby databases, minimizing the down time of the primary database for planned and unplanned outages.



Securing Your Logical Standby Database

• Configure the database guard to control user access to tables.

• ALTER DATABASE GUARD command keywords:– ALL: Prevents users from making changes to any

data in the database– STANDBY: Prevents users from making changes to

any data maintained by Data Guard SQL Apply– NONE: Normal security

• Query GUARD_STATUS column in V$DATABASE.• Database guard level is set to ALL by broker

automatically on the logical standby database.• Database guard level applies to all users except

SYS.

Securing Your Logical Standby DatabaseYou can control user access to tables in a logical standby database by using the ALTERDATABASE GUARD command to configure the database guard.By default, it is not possible for a nonprivileged user to modify data on a Data Guard SQL Apply database. This is because the database guard is automatically set to ALL. With this level of security, only the SYS user can modify data. If you are not using the broker, you can set the security level to the STANDBY level. In this case, users are able to modify data that is not maintained by the logical apply engine. A security level of NONE permits any user to access the standby database as long as theyhave the correct privileges.When creating a logical standby database manually with SQL commands, you must issue the ALTER DATABASE GUARD ALL command before opening the database. Failure to do so will allow jobs that are submitted through DBMS_JOB.SUBMIT to be scheduled and to potentially modify tables in the logical standby database.



Preparing to Create aLogical Standby Database

1. Check for unsupported data types. 2. Be aware of unsupported DDL commands.3. Ensure row uniqueness. 4. Verify that the primary database is configured for

ARCHIVELOG mode.5. Enable supplemental logging.6. Create an alternate tablespace for logical standby

system tables (optional).

Perform the following steps on the primary database before creating a logical standby database:

Preparing to Create a Logical Standby DatabaseWhen creating a logical standby database, you must take several actions before you begin. The following pages discuss these steps in detail.



Unsupported Data Types

• BFILE, ROWID, and UROWID

• User-defined types• Object types REFs• Varrays• Nested tables• XMLtype

Unsupported Data TypesEnsure that your logical standby database can support the data types of the database objects that are defined in your primary database. If the primary database contains unsupported tables, log apply services automatically exclude these tables when applying redo data to the logical standby database.



Unsupported Objects

• Tables and sequences in the SYS schema• Tables with unsupported data types• Tables using table compression• Tables used to support functional indexes• Tables used to support materialized views• Global temporary tables• Index-organized tables (IOTs) with overflows and

LOB columns

Unsupported ObjectsRefer to Oracle Data Guard Concepts and Administration for additional information on unsupported data types and objects.



Checking for Tables with Unsupported Data Types

Query DBA_LOGSTDBY_UNSUPPORTED on the primary database for tables with unsupported data types:

SQL> desc DBA_LOGSTDBY_UNSUPPORTED

Name Null? Type-------------- -------- -------------OWNER NOT NULL VARCHAR2(30)TABLE_NAME NOT NULL VARCHAR2(30)COLUMN_NAME NOT NULL VARCHAR2(30)DATA_TYPE VARCHAR2(106)

Checking for Tables with Unsupported Data TypesYou can query the DBA_LOGSTDBY_UNSUPPORTED data dictionary view to see all of the tables that contain data types that are not supported by logical standby databases. These tables are not maintained (do not have DML applied) in the logical standby database. Any changes made to unsupported data types, tables, sequences, or views on the primary database are not propagated to the logical standby database, nor is an error message returned.It is a good idea to query this view on the primary database to ensure that those tables necessary for critical applications are not in this list before you create the logical standby database. If the primary database includes unsupported tables that are critical, consider using a physical standby database instead.Note: This view does not show any tables from the SYS schema because changes to the SYSschema object are not applied to the logical standby database. In addition, this view does not show tables with table compression.



Unsupported DDL Commands

• ALTER DATABASE

• ALTER SESSION

• ALTER MATERIALIZED VIEW

• ALTER MATERIALIZED VIEW LOG

• ALTER SYSTEM

• CREATE CONTROL FILE

• CREATE DATABASE

• CREATE DATABASE LINK

• CREATE PFILE FROM SPFILE

• CREATE SCHEMA AUTHORIZATION

• CREATE MATERIALIZED VIEW

• CREATE MATERIALIZED VIEW LOG

• CREATE SPFILE FROM PFILE

• DROP DATABASE LINK

• DROP MATERIALIZED VIEW

• DROP MATERIALIZED VIEW LOG

• EXPLAIN

• LOCK TABLE

• SET CONSTRAINTS

• SET ROLE

• SET TRANSACTION

Unsupported DDL CommandsNot all data definition language (DDL) commands that are executed on the primary database are applied to the logical standby database. If you execute any of these commands (shown in the slide) on the primary database, they are not executed on any logical standby database in your configuration. You must execute them on the logical standby database to maintain consistency between the primary database and the logical standby database.



Ensuring Unique Row Identifiers

• Query DBA_LOGSTDBY_NOT_UNIQUE on the primary database to find tables without a unique identifier:

• BAD_COLUMN possible values:– Y: Data type is unbounded.– N: Table contains enough column information.

SQL> desc DBA_LOGSTDBY_NOT_UNIQUEName Null? Type-------------- -------- ------------OWNER NOT NULL VARCHAR2(30)TABLE_NAME NOT NULL VARCHAR2(30)BAD_COLUMN VARCHAR2(1)

Ensuring Unique Row IdentifiersBecause the row IDs on a logical standby database might not be the same as the row IDs on the primary database, a different mechanism must be used to match the updated row on the primary database to its corresponding row on the logical standby database. Primary keys and unique indexes can be used to match the corresponding rows. It is recommended that you add a primary key or a unique index to tables on the primary database (whenever appropriate and possible) to ensure that SQL Apply can efficiently apply data updates to the logical standby database.You can query the DBA_LOGSTDBY_NOT_UNIQUE view to identify tables in the primary database that do not have a primary key or unique index with NOT NULL columns. Issue the following query to display a list of tables that SQL Apply might not be able to uniquely identify:

SQL> SELECT OWNER, TABLE_NAME,BAD_COLUMN 2 FROM DBA_LOGSTDBY_NOT_UNIQUE3 WHERE TABLE_NAME NOT IN 4 (SELECT TABLE_NAME FROM DBA_LOGSTDBY_UNSUPPORTED);


Ensuring Unique Row Identifiers (continued)The key column in this view is BAD_COLUMN. If this view returns a row for a given table, you may want to consider adding a primary or unique key constraint on the table.A value of Y indicates that the table does not have a primary or unique constraint and that the column is defined using an unbounded data type, such as CLOB. If two rows in the table match except for values in their LOB column, then the table cannot be maintained properly and SQL Apply stops. A value of N indicates that the table does not have a primary or unique constraint but that it contains enough column information to maintain the table in the logical standby database. However, the log transport services and log apply services run more efficiently if you add a primary key. You should consider adding a disabled RELY constraint to these tables (as described later in this lesson).



Adding a Disabled Primary Key RELY Constraint

You can add a disabled RELY constraint to uniquely identify rows:

SQL> ALTER TABLE hr.employees2 ADD PRIMARY KEY (employee_id, last_name)3 RELY DISABLE;

Adding a Disabled Primary Key RELY ConstraintIf your application ensures that the rows in a table are unique, you can create a disabled primary key RELY constraint on the table without incurring the overhead of maintaining a primary key on the primary database.The RELY constraint tells the system to log the named columns (in this example, employee_id and last_name) to identify rows in this table. Be careful to select columns for the disabled RELY constraint that uniquely identify the row. If the columns selected for the RELY constraint do not uniquely identify the row, SQL Apply does notapply redo information to the logical standby database.Note: For this example, assume that the HR.EMPLOYEES table does not have a primary key.



Supplemental Logging

• Adds supplemental data to the log stream• Three levels of database supplemental logging:

– Full: Enables database-wide, before-image logging of primary keys or unique indexes for all updates

– Minimal: Minimal amount of information needed for LogMiner to identify, group, and merge the redo operations that are associated with DML changes

– None: No additional redo information added to the redo stream

• SQL Apply requires full supplemental logging.

Supplemental LoggingFor logical standby to work properly, the logs must contain enough information for the standby database to be created. The supplemental_db_logging clauses of the ALTER DATABASE command instruct Oracle Database to add or stop adding supplemental data to the log stream. Supplemental logging must be enabled on the primary database to support a logical standby database. Because an Oracle Database only logs the columns that were modified, this is not always sufficient to uniquely identify the row that changed, and additional (supplemental) information must be put into the stream of redo data. The supplemental information that is added to the redo data helps SQL Apply correctly identify and maintain tables in the logical standby database. Supplemental logging can be enabled as follows:

• Full supplemental logging (or identification key logging) enables database-wide, before-image logging of primary keys or unique indexes (in the absence of primary keys) for all updates. With this type of logging, an application can identify updated rows logically rather than resorting to row IDs. This type of logging is required by SQL Apply.


Supplemental Logging (continued)On the primary database, issue the following statement to add primary key and unique index information to the archived redo log file:

SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA 2 (PRIMARY KEY, UNIQUE INDEX) COLUMNS;

• Minimal supplemental logging logs the minimal amount of information that is needed for LogMiner to identify, group, and merge the redo operations that are associated with DML changes. It ensures that LogMiner (and any products building on LogMiner technology) has sufficient information to support chained rows and various storage arrangements, such as cluster tables. Issue the following statement to enable minimal supplemental logging:

SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

Note: The default for supplemental logging is None.



Enabling Supplemental Logging

• Data Guard broker automatically enables supplemental logging.

• Manually enable full supplemental logging before your create your logical standby:

• Verify that the following columns in V$DATABASEcontain a YES value:– SUPPLEMENTAL_LOG_DATA_MIN

– SUPPLEMENTAL_LOG_DATA_PK

– SUPPLEMENTAL_LOG_DATA_UI

SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA2 (PRIMARY KEY, UNIQUE INDEX) COLUMNS;

SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;

Enabling Supplemental LoggingYou must enable full supplemental logging before you create the logical standby database. The reason is that the logical standby database cannot use archived redo logs that contain both supplemental log data and nonsupplemental log data. Note: Enterprise Manager automatically enables supplemental logging when you create the logical standby database.The following columns in the V$DATABASE view have a YES value after supplemental logging has been enabled. YES represents the following for the respective columns:• SUPPLEMENTAL_LOG_DATA_MIN: LogMiner has sufficient information to support

chained rows and various storage arrangements.• SUPPLEMENTAL_LOG_DATA_PK: All columns of the primary key are placed in the

redo log whenever there is an update.• SUPPLEMENTAL_LOG_DATA_UI: If any unique key columns are modified, all other

columns belonging to the unique key are also logged.Note: If you enable full supplemental logging on your primary database and you have already created physical standby databases, then you must enable supplemental logging on each physical standby database to ensure that future switchovers work correctly.



Verifying Values ofInitialization Parameters

Verify the values for the following initialization parameters on the primary database :• PARALLEL_MAX_SERVERS

• LOG_PARALLELISM

• SHARED_POOL_SIZE

Verifying Values of Initialization Parameters Verify the values of the following initialization parameters on the primary database before creating the logical standby database:• PARALLEL_MAX_SERVERS: Value must be set to 5 or greater. The recommended

value is 9. The SQL Apply Service on the logical standby site uses several parallel processes when applying the SQL to the logical database.

• LOG_PARALLELISM: Value must be set to 1. This is the default value. If this value is changed, LogMiner on the logical standby site cannot read the redo logs.

• SHARED_POOL_SIZE: Value should be 160 MB or greater. This is a recommendation. Your configuration may operate with a lower value, but in a production environment a lower value may cause performance degradation.



Creating a Logical Standby Database with Enterprise Manager

Click “Add Standby Database.”

Creating a Logical Standby Database with Enterprise ManagerThe following series of slides shows you how to add a logical standby database to an existing configuration.First, click Add Standby Database to invoke the Add Standby Database Wizard.



Using the Add Standby Database Wizard

Select "Create a new logical standby database."

Click Continue.

Using the Add Standby Database WizardSelect “Create a new logical standby database” on the Add Standby Database page, and then click continue.



Step 1: Specifying the Backup Type

Step 1: Specifying the Backup TypeOn the Backup Type page of the wizard, select one of two backup operations to use to create the standby database (as you did when creating a physical standby database).When you create a logical standby database, the wizard also identifies tables that cannot be supported in your logical standby database and displays a list on the Backup Type page.Click Next to continue.



Step 2: Specifying the Backup Options

Step 2: Specifying the Backup OptionsOn the Backup Options page, specify the parameters that are required to perform a new backup of the primary database or to access an existing backup.See the lesson titled “Creating a Configuration with Enterprise Manager” for additional information about the parameters on the Backup Options page.Click Next to continue.



Step 3: Selecting the Oracle Home –Instance Name

Step 3: Selecting the Oracle Home – Instance NameOn the Standby Oracle Home page, specify the parameters that are required to create the standby database and select the Oracle home in which to create the standby database. The standby database can be created in any Oracle home that has been discovered by Oracle Enterprise Manager. Only Oracle homes on hosts that match the architecture and version of the primary host are shown.Click Next to continue.



Step 4: Specifying the Standby Database File Locations – Access Method

Step 4: Specifying the Standby Database File Locations – Access MethodOn the File Locations page, specify the location for the standby database files and customize other selections based on whether the standby database is being created on a different host than the primary database. Note: The Backup File Access section appears only when the standby database is being created on a host other than the primary database. In this case, you must choose a method to make the primary backup files accessible to the standby host.



Step 4: Specifying the Standby Database File Location – File Locations

Step 4: Specifying the Standby Database File Location – File LocationsWhen the primary and standby databases are on the same host, all standby database files are put in an Optimal Flexible Architecture (OFA) directory structure by default.When the primary and standby databases are on different hosts, you can use the Standby Database File Locations section to put all the standby database files in an OFA directory structure, or to keep file names and locations the same as the primary database.You can optionally change the locations of individual standby database files by clicking Customize, which displays the File Locations Customize page.Data Guard automatically adds configuration information for the new standby database to the listener.ora and tnsnames.ora files in the directory that is specified in the Network Configuration File Location section. The default location is the network administration directory of the standby database Oracle home.



Step 5: Specifying Standby Database Configuration Parameters

Step 5: Specifying Standby Database Configuration ParametersOn the Standby Configuration page, you can specify configuration parameters for the standby database. The configuration parameters include the instance name, service provider name, target name, and standby archive location. The default values are based on corresponding primary database settings.When you create a new physical database, the following parameters must be configured:

• Database Name: This field appears only when you are creating a new logical standby database. (Physical standby databases use the same database name as the primary.) A default database name is provided; you can specify any name that conforms to Oracle naming conventions.

• Database Unique Name: Specify a value for the DB_UNIQUE_NAME parameter. This name must be unique in the Data Guard configuration. Note: This field appears only if you are creating a new physical standby database and the primary database is an Oracle10g database.

• Target Name: Specify a name for Enterprise Manager to use for the new standby database. This name appears in the list of database targets maintained by Enterprise Manager. It is recommended that this name be the same as the database unique name.



Step 6: Reviewing the Configuration Information

Step 6: Reviewing the Configuration InformationThe Review page of the wizard displays a summary of your selections and lists the parameters to be used to create the new standby database.The new standby database is created in the background by an Oracle Enterprise Manager job. The name of the job that is submitted is provided at the top of the page.When you click Finish, the Processing page appears. This page tracks each step through the submission of the standby creation job. After the job submission is complete, you see the Data Guard Overview page, where you can monitor the progress of the standby creation job.



Standby Database Creation Processing

Standby Database Creation ProcessingYou can view the progress of the Add Standby Database process on the Processing page. When the process completes, Enterprise Manager displays the Data Guard Overview page.



Resolving a Failed or Canceled Configuration Creation

• On the primary node:1. Stop the Data Guard broker processes.2. Remove the Data Guard configuration files.

• On the standby node:1. Shut down the standby database.2. Remove the initialization files for the standby

database.3. Remove the entry pertaining to the standby

database from the Oracle Net listener file.4. Stop and restart the Oracle Net listener.5. Remove the standby database data files and online

log files.

Resolving a Failed or Canceled Configuration CreationIf the Add Standby Database Wizard failed or was canceled when creating a configuration with a new standby database, you may need to perform the following cleanup tasks before you can reattempt the process. Some, none, or all of the cleanup tasks may be necessary to clean up the results of the failed or canceled operation. On the primary node:

1. Stop the Data Guard broker processes. To stop the processes, connect to the primary database and set the DG_BROKER_START system parameter to FALSE.

2. Remove the Data Guard configuration files. Delete these files with the appropriate delete command for the operating system.

On the standby node: 1. Shut down the standby database. 2. Remove the initialization files for the standby database. Delete these files with the

appropriate delete command for the operating system.3. Remove the entry pertaining to the standby database from the Oracle Net listener file

(listener.ora) in the Oracle home for the standby database.4. Stop and restart the Oracle Net listener.5. Remove the standby database data files and online log files. The commands that you

use to remove the files depend on where the files are located on the standby node.



Summary

In this lesson you should have learned how to:• Explain the advantages of a logical standby

database• Decide when to use a logical standby database• Create a logical standby by using Enterprise

Manager




This practice covers the following topics:• Creating a logical standby database using the

Add Standby Database Wizard• Verifying the configuration


Creating a Logical Standby Databaseby Using SQL



Objectives

After completing this lesson, you should be able to use SQL commands to create a logical standby database.



Preparing to Create aLogical Standby Database

As preparation for creating a logical standby database, perform the following steps on the primary database:• Check for unsupported data types. • Be aware of unsupported DDL commands.• Ensure row uniqueness. • Verify that the primary database is configured for

ARCHIVELOG mode.• Enable supplemental logging.• (Optional) Create an alternate tablespace for

logical standby system tables. • Check the values of initialization parameters.

Preparing to Create a Logical Standby DatabaseThese tasks were covered in the “Data Guard SQL Apply Architecture” lesson. They are presented again as a reminder that they must be performed whether you are using Enterprise Manager or SQL commands to create a logical standby database.Be sure to check that the initialization parameters have the following values:• PARALLEL_MAX_SERVERS > 5• LOG_PARALLELISM = 1• SHARED_POOL_SIZE: 160 MB or higher (recommended)



Creating a Logical Standby Database

To create a logical standby database by using SQL commands:1. Create a physical standby database.2. Prepare the primary database to support a logical

standby database.3. Prepare to transition to a logical standby

database.4. Start the logical standby database.5. Verify that the logical standby database is

performing properly.

Creating a Logical Standby DatabaseEach of these steps is outlined in detail in the remainder of this lesson.



Step 1: Create a PhysicalStandby Database

a. Create a physical standby database.b. Ensure that the physical standby database is

caught up to the primary database.

Step 1: Create a Physical Standby DatabaseYou create a logical standby database by first creating a physical standby database. Then you transition the physical standby database into a logical standby database. To create the physical standby database:

a. Create a physical standby database as described in the lesson titled “Creating a Physical Standby Database by Using SQL.”

b. Ensure that the physical standby database is caught up to the primary database by allowing recovery to continue until the physical standby database is consistent with the primary database, including all database structural changes (such as adding or dropping data files).



Step 2: Prepare the Primary Database to Support a Logical Standby Database

a. Ensure that supplemental logging is enabled.

b. Enable supplemental logging (if necessary).

SQL> SELECT SUPPLEMENTAL_LOG_DATA_PK 2 AS PK_LOG, 3 SUPPLEMENTAL_LOG_DATA_UI AS UI_LOG 4 FROM V$DATABASE;

SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA 2 (PRIMARY KEY, UNIQUE INDEX) COLUMNS;

Step 2: Prepare the Primary Database to Support a Logical Standby DatabasePerform the following steps to ensure that supplemental logging is enabled:

a. Supplemental logging must be enabled on the primary database to support a logical standby database. Determine whether supplemental logging is enabled on the primary database by querying the V$DATABASE view:

SQL> SELECT SUPPLEMENTAL_LOG_DATA_PK AS PK_LOG, 2> SUPPLEMENTAL_LOG_DATA_UI AS UI_LOG 3> FROM V$DATABASE;

A value of YES in the columns indicates that supplemental logging is enabled.b. If supplemental logging is not enabled, issue the following statement to add primary

key and unique index information to the archived redo log file:SQL> ALTER DATABASE ADD SUPPLEMENTAL LOG DATA

2 (PRIMARY KEY, UNIQUE INDEX) COLUMNS;



Step 2: Prepare the Primary Database to Support a Logical Standby Database

c. Prepare the primary database for role transitions by setting LOG_ARCHIVE_DEST_n parameters appropriately.

d. Set the value of UNDO_RETENTION to 3600.

Step 2: Prepare the Primary Database to Support a Logical Standby Database (continued)

c. To transition the primary database to the logical standby role, you must modify the initialization parameters on the primary database so that no parameters need to change after a role transition.Use the ALTER SYSTEM SET SCOPE=BOTH command to dynamically set the LOG_ARCHIVE_DEST_n initialization parameters.

d. Set the UNDO_RETENTION initialization parameter to 3600. The UNDO_RETENTION parameter specifies (in seconds) the amount of committed undo information to retain in the database. The value of 3600 is recommended for best results when building a LogMiner dictionary for the logical standby database.



Step 3: Prepare to Transition to a Logical Standby Database

a. Ensure that supplemental logging is enabled on the standby database.

b. Prepare an initialization parameter file for the logical standby database.

c. Shut down the logical standby database.d. Create a control file for the logical standby

database.e. Copy the control file to the logical standby

database system.

Step 3: Prepare to Transition to a Logical Standby DatabaseUse the following procedure to prepare to transition to a logical standby database:

a. Enabling supplemental logging on the logical standby database now rather than later is beneficial to prepare the database for future role transitions. Perform the steps listed earlier in this lesson for the primary database on the logical standby database.

b. Modify the LOG_ARCHIVE_DEST_n parameters and add the PARALLEL_MAX_SERVERS parameter to the initialization parameter file (PFILE) that you created for your physical standby database. You need to modify the LOG_ARCHIVE_DEST_n parameters because logical standby databases are open databases that generate redo data and have multiple log files (online redo log files, archived redo log files, and standby redo log files). It is good practice to specify separate local destinations for:

- Archived redo log files that store redo data that is generated by the logical standby database

- Archived redo log files that store redo data that is received from the primary database

Set PARALLEL_MAX_SERVERS to a minimum value of 9; do not set it to a value less than 5.


Step 3: Prepare to Transition to a Logical Standby Database (continued)c. Shut down the logical standby database by issuing the following command:

SQL> SHUTDOWN IMMEDIATE;

You mount the logical standby database using the new initialization parameter file in a later step.

d. On the primary database system, issue the ALTER DATABASE CREATE LOGICALSTANDBY CONTROLFILE statement to create a control file for the standby database as shown in the following example. Be sure to include the LOGICAL keyword.

SQL> ALTER DATABASE CREATE LOGICAL STANDBY CONTROLFILE 2 AS '/tmp/site2.ctl';

e. Use an operating system copy utility to copy the standby control file from the primary database system to the logical standby database system.



Step 4: Start the Logical Standby Database

a. Start and mount the logical standby database.b. Prepare the logical standby database for SQL

Apply:

c. Activate the logical standby database:

d. Reset the database name of the logical standby database by using the DBNEWID utility.

SQL> ALTER DATABASE RECOVER 2 MANAGED STANDBY DATABASE;

SQL> ALTER DATABASE ACTIVATE 2 STANDBY DATABASE;

Step 4: Start the Logical Standby DatabasePerform the following steps to start, mount, and activate the logical standby database and SQL Apply.

a. On the logical standby database, issue the STARTUP MOUNT command to start the instance and mount the database.

b. On the logical standby database, issue the following command to prepare it for SQL Apply:

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE;

c. After the command issued in step (b) has completed execution, issue the following command to activate the database as a logical standby database:

SQL> ALTER DATABASE ACTIVATE STANDBY DATABASE;

d. Shut down the instance, restart it, and mount the database in preparation for executing the DBNEWID utility. Invoke the Oracle DBNEWID utility on the logical standby database to change the database name and shut down the database as shown in the following example:

nid TARGET=SYS/password@boston DBNAME=bostonNote: You must re-create the password file after running the Oracle DBNEWID (nid) utility.



Step 4: Start the Logical Standby Database

e. Change the logical standby database name in the parameter file.

f. Change the logical standby database global name:

g. Create a new temporary file for the logical standby database.

h. Start SQL Apply:

SQL> ALTER DATABASE RENAME GLOBAL_NAME TO 2 new_global_name;

SQL> ALTER DATABASE START 2 LOGICAL STANDBY APPLY;

Step 4: Start the Logical Standby Database (continued)e. Modify the DB_NAME initialization parameter in the initialization parameter file.

Connect to an idle instance of the logical standby database. Then create a server parameter file for the standby database from the text initialization parameter file, as in the following example:

SQL> CREATE SPFILE FROM PFILE=initboston.ora;Restart the logical standby database instance and open the logical standby database with the RESETLOGS option.

f. Execute the following command to change the logical standby database global name:SQL> ALTER DATABASE RENAME GLOBAL_NAME TO new_global_name;

g. Create new temporary files on the logical standby database as follows. First identify tablespaces that contain temporary files:

SQL> SELECT TABLESPACE_NAME FROM DBA_TABLESPACES2 WHERE CONTENTS = 'TEMPORARY';

For each tablespace identified in the previous query, add a new temporary file to the standby database with the ALTER TABLESPACE command.

h. Issue the following statement to begin applying redo data to the logical standby database:

SQL> ALTER DATABASE START LOGICAL STANDBY APPLY;



Step 5: Verify That the Logical Standby Database Is Performing Properly

a. Verify that the archived redo log files were registered:

b. Begin sending redo data to the standby database:

c. Query the DBA_LOGSTDBY_LOG view to verify that the archived redo log files were registered.

SQL> SELECT SEQUENCE#, FIRST_TIME, NEXT_TIME, 2 DICT_BEGIN, DICT_END3 FROM DBA_LOGSTDBY_LOG ORDER BY SEQUENCE#;


Step 5: Verify That the Logical Standby Database Is Performing ProperlyAfter you create your logical standby database and set up log transport services and log apply services, you should verify that redo data is being transmitted from the primary database and applied to the standby database. Perform the following steps to verify that the logical standby database is functioning properly:

a. Connect to the logical standby database and query the DBA_LOGSTDBY_LOG view to verify that the archived redo log files were registered on the logical standby system:

SQL> SELECT SEQUENCE#, FIRST_TIME, NEXT_TIME, DICT_BEGIN, 2 DICT_END FROM DBA_LOGSTDBY_LOG ORDER BY SEQUENCE#;

b. Connect to the primary database and issue the following command to begin sending redo data to the standby database:

SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;c. Connect to the logical standby database and re-query the DBA_LOGSTDBY_LOG view

as shown in step a. This enables you to verify that the new archived redo log files were registered.



Step 5: Verify That the Logical Standby Database Is Performing Properly

d. Verify that redo data is being applied correctly:

e. View the V$LOGSTDBY view to see current SQL Apply activity:

f. Check the overall progress of SQL Apply:

SQL> SELECT NAME, VALUE FROM V$LOGSTDBY_STATS 2 WHERE NAME = 'coordinator state';

SQL> SELECT TYPE, HIGH_SCN, STATUS 2 FROM V$LOGSTDBY;

SQL> SELECT APPLIED_SCN, NEWEST_SCN 2 FROM DBA_LOGSTDBY_PROGRESS;

Step 5: Verify That the Logical Standby Database Is Performing Properly (continued)

d. On the logical standby database, query the V$LOGSTDBY_STATS view to verify that redo data is being applied correctly:

SQL> SELECT NAME, VALUE FROM V$LOGSTDBY_STATS 2 WHERE NAME = 'coordinator state';

A value of INITIALIZING in the VALUE column indicates that log apply services are preparing to begin SQL Apply, but data from the archived redo log files is not being applied to the logical standby database.

e. Query the V$LOGSTDBY view on the logical standby database to see a current snapshot of SQL Apply activity. A text message describing the current activity of each process that is involved in reading and applying changes is displayed.

f. Query the DBA_LOGSTDBY_PROGRESS view on the logical standby database to check the overall progress of SQL Apply:




Additional Configuration Tasks

Perform the following tasks as appropriate for your configuration:• Configure standby redo logs.• Enable Flashback Database.• Upgrade the data protection mode.

Additional Configuration TasksPerform the following tasks as appropriate for your logical standby database:

• Configure standby redo logs: Standby redo logs are required for standby databases running in maximum protection mode and maximum availability mode. However, configuring standby redo logs is recommended on all standby databases because, during a failover, Data Guard can recover and apply more redo data from standby redo log files than from the archived redo log files alone. The standby redo logs should exist on both primary and standby databases and have the same size and names.

• Enable Flashback Database: Flashback Database eliminates the need to re-create the primary database after a failover. Flashback Database is similar to conventional point-in-time recovery in its effects, enabling you to return a database to its state at a time in the recent past. Flashback Database is faster than point-in-time recovery because it does not require restoring data files from backup or the extensive application of redo data. You can enable Flashback Database on the primary database, the standby database, or both.

• Upgrade the data protection mode: The Data Guard configuration is initially set up in maximum performance mode (the default).



Summary

In this lesson, you should have learned how to use SQL commands to create a logical standby database.


Switchover and Failover



Objectives

After completing this lesson, you should be able to do the following:• Explain the database roles• Perform a switchover• Perform a failover• Use Flashback Database after a failover



Types of Roles in an Oracle Data Guard Configuration

There are two types of roles in an Oracle Data Guard configuration:• User role: Identifies the group and determines the

privileges that a user is assigned• Database role: Identifies what role (primary or

standby) the database plays in a Data Guard configuration

SQL> SELECT database_role FROM V$DATABASE; DATABASE_ROLE----------------LOGICAL STANDBY

Types of Roles in an Oracle Data Guard ConfigurationUser roles are named groups of related privileges that you grant to users or other user roles. User roles are designed to ease the administration of the end-user system and schema object privileges. Database roles identify what “part” the database is “playing” in the Data Guard configuration. A database can be in one of two roles:

• Primary• Standby

A database that is in the standby role is one of the following types:• Physical standby• Logical standby



Role Management Services

• A database operates in one of two mutually exclusive roles in a Data Guard configuration:– Primary role: The database is operating in the

primary role, and log transport services are shipping redo to the standby databases.

– Standby role: The database is operating in the standby role, and log apply services are applying the archived redo logs to the standby database.

• With role management services, you can change these roles dynamically.

Role Management ServicesYou can use role management services to change the primary and standby roles dynamically as a planned transition called a switchover operation, or as a result of a database failure through a failover operation. For example, you might perform a switchover operation to transition the primary database to the standby role and transition a standby database to the primary role to perform routine maintenance tasks.



Role Transitions: Switchover and Failover

• Not automatically invoked• Switchover

– Planned role reversal– Used for OS or hardware maintenance

• Failover– Unplanned role reversal– Used in an emergency– Minimal or no data loss depending on the

data protection mode

Role Transitions: Switchover and FailoverSwitchover and failover operations are not invoked automatically. You must initiate switchover or failover operations by using a SQL statement or by using the Data Guard GUI or Data Guard broker command-line interface (CLI).SwitchoverYou can use the switchover feature to switch the role of the primary database to one of the available standby databases. The chosen standby database becomes the primary database, and the original primary database then becomes a standby database. There is no need to re-create any of the databases in the switchover operation. There is no data divergence between the original and the new primary database after the successful completion of the database switchover.


Role Transitions: Switchover and Failover (continued)FailoverYou invoke a failover operation when a catastrophic failure occurs on the primary database, and there is no possibility of recovering the primary database in a timely manner. During a failover operation, the incapacitated primary database is removed from the Data Guard environment and a standby database assumes the primary database role. You invoke the failover operation on the standby database that you want to fail over to the primary role.You should not fail over to a standby database except in an emergency, because the failover operation may result in the loss of application data. After you perform a failover operation, there is no going back.



Role Transition Decision Tree

Are you performing a planned role transition so that you can perform hardware or software maintenance on the system that currently hosts the primary database?

Switchover to best available standby database.

Yes

Can you run crash recovery to repair the primary database in a timely manner?

Yes Repair primary database.

No

No

Failover to best available standby database.

Role Transition Decision TreeThe goal of a role transition (switchover or failover) is to bring the new primary database online as quickly as possible with no data loss or with the least possible data loss. The decision tree shown in the slide can help you choose the role transition operation that best minimizes down time and the risk of data loss. In general, you should always consider performing crash recovery to repair the primary database or performing a switchover before you consider performing a failover.Repairing the primary database may be faster than transitioning a standby database to the primary role, even when you are using a no-data-loss environment. If you can repair the primary database, you also do not have to reconfigure client applications to connect to a new database. However, if the repair operation results in any data loss, you may need to re-create all other standby databases in the configuration from a backup of the repaired primary database.In general, the best standby database to transition to is a physical standby database that has the most redo applied to it.



Switchover

• Transitions the roles of the primary and standby databases

• No resetting of the online redo logs of the new primary database

• No data loss

SwitchoverA switchover operation transitions the primary database to the standby role and transitions the standby database to the primary role, without resetting the online redo logs of the new primary database. If the switchover operation involves a physical standby database, both the primary database and the physical standby database that is switching over to the primary role must be shut down and restarted. However, there is no need to shut down and restart any other standby databases that are not participants in the switchover operation. If the switchover operation involves a logical standby database, there is no need to shut down and restart either the primary database or any of the standby databases. Logical standby databases do not need to be shut down and restarted.



Switchover: Before

Standbydatabase

Read/writetransactions

Primarydatabase

San FranciscoBoston

Oracle Net

Application

Application

Read-only reports

Switchover: BeforeFor example, assume that the primary database is located in San Francisco and the physical standby database is located in Boston. Switchovers are initiated only on the primary database. They cannot be initiated from the standby database.



Switchover: After

Standbydatabase


Primarydatabase

Application

Application

Read-only reports

San FranciscoBoston

Oracle Net

Switchover: AfterAfter the switchover completes, each database has the role opposite to the one that it had before the switchover. In our example, Boston is now the primary database and San Francisco is the standby database.Data Guard does not automatically switch over sessions from one database to the other, so active sessions for each system need to reconnect.



Standby Redo Logs and Switchovers

Standby redo logs should be configured on the primary database to ease switchovers.

Redo shipment

RFS

Standbyredo logs

Online redo logs

Primarydatabase

Standbydatabase

Standbyredo logs

Standby Redo Logs and SwitchoversStandby redo log configuration should be identical on the primary database and on any physical standby databases. Even though the standby redo logs are not used when the database is in the primary role, configuring the standby redo logs on the primary database is recommended in preparation for an eventual switchover operation.



Preparing for a Switchover

Verify the following in preparation for the switchover operation:• Network connectivity between the primary and

standby locations• Standby database that will become the new

primary database must be in ARCHIVELOG mode.

Preparing for a SwitchoverEach location in the Data Guard configuration should have connectivity through Oracle Net to the primary database and to all associated standby databases.The database that you are planning to switch over to must be in ARCHIVELOG mode. However, to give yourself the full benefit of your configuration, it is best to have all standby databases configured in ARCHIVELOG mode. You then have the option of using all of your standby databases when you want to perform a switchover.



Performing a Switchover with Enterprise Manager

Select the database and click Switchover.

Performing a Switchover with Enterprise ManagerThe following tasks are performed when Enterprise Manager is used for the switchover:

a. A check is made to ensure that the primary database and standby database are not currently in an error status condition and that broker management of the primary database is enabled and online.

b. Any active sessions connected to the primary database are automatically closed during the switchover.

c. The primary database is first changed to the standby role, and then the standby database is changed to the primary role.

d. If the switchover target is a physical standby database, the target and primary databases are each restarted.

To initiate a switchover by using Enterprise Manager:1. On the Data Guard page, select the standby database that you want to become the

primary database.2. Click Switchover.




Click Yes to confirm.

Performing a Switchover Using Enterprise Manager (continued)3. The Data Guard Switchover Confirmation page appears.4. You can view active sessions by clicking the Browse Primary Database Sessions link.5. Click Yes to continue with the switchover, or click No to cancel.

You cannot cancel the switchover operation after it has begun.




Performing a Switchover Using Enterprise Manager (continued)The Data Guard Switchover processing page displays the progress of the switchover operation as it performs the following steps:

• Switch roles between the primary and standby databases. If the switchover target is a physical standby database, it is restarted along with the primary database.

• Wait for the Data Guard broker to complete the initialization tasks required to switch the database roles.

You can view the database alert log of the primary and standby databases by clicking the respective “View alert log” links. A new browser window opens with the content of the alert log.After the switchover operation is complete, you are returned to the Data Guard page.



Performing a Switchover to a Physical Standby by Using SQL

Perform these steps only if you are not using the Data Guard broker.On the original primary database:1. Verify that it is possible to perform a switchover

operation.2. Initiate the switchover operation on the primary

database:

3. Shut down and restart the instance.

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO 2 PHYSICAL STANDBY;

Performing a Switchover to a Physical Standby by Using SQLYou can perform a switchover using SQL, as described in the following steps. You should not execute these steps when managing your configuration with the Data Guard broker. Consider using the Data Guard broker to automate and simplify the switchover procedure.Execute steps 1 through 3 on the original primary database:

1. Query the SWITCHOVER_STATUS column of the V$DATABASE view on the primary database to verify that it is possible to perform a switchover operation. A TO STANDBY value in the SWITCHOVER_STATUS column indicates that it is possible to switch the primary database to the standby role.

2. To transition the primary database to a physical standby database role, execute the following SQL statement:

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO2 PHYSICAL STANDBY WITH SESSION SHUTDOWN WAIT;

The WAIT option specifies that control is not returned to you until the statement completes.

3. Shut down the instance and restart it without mounting the database:SQL> SHUTDOWN IMMEDIATE;SQL> STARTUP NOMOUNT;



Performing a Switchover to a Physical Standby by Using SQL

On the original physical standby database:4. Verify the switchover status in the V$DATABASE

view.5. Switch the physical standby database role to the

primary role.6. Shut down and restart the new primary database.7. Begin archiving logs to the physical standby

database.

Performing a Switchover to a Physical Standby by Using SQL (continued)Execute steps 4 through 7 on the original standby database:

4. After you switch the primary database to the standby role and the switchover notification has been received by the standby database, you should verify that the switchover notification has been processed by the standby database by querying the SWITCHOVER_STATUS column of the V$DATABASE fixed view on the standby database. You should see a value of TO_PRIMARY.

5. Execute the following SQL statement on the physical standby database that you want to switch to the primary role:

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

6. Shut down and restart the new primary database.SQL> SHUTDOWN;SQL> STARTUP;

The selected physical standby database is now transitioned to the primary database role. There is no need to shut down and restart any other standby databases that were online at the time of the switchover operation.

7. Issue the following statement on the new primary database to start redo transport:SQL> ALTER SYSTEM SWITCH LOGFILE;



Performing a Switchover to a Logical Standby by Using SQL

On the original primary database:1. Verify that it is possible to perform a switchover.2. Prepare the primary database for the switchover:SQL> ALTER DATABASE PREPARE TO SWITCHOVER

2 TO LOGICAL STANDBY;

Performing a Switchover to a Logical Standby by Using SQLWhen you perform a switchover that changes roles between a primary database and a logical standby database, you must always initiate the switchover on the primary database and complete it on the logical standby database.Perform steps 1 and 2 on the original primary database:

1. Query the SWITCHOVER_STATUS column of the V$DATABASE view on the primary database to verify that it is possible to perform a switchover operation. A TO STANDBY or SESSIONS ACTIVE value in the SWITCHOVER_STATUScolumn indicates that it is possible to switch the primary database to the standby role.

2. Issue the following SQL statement to prepare the current primary database for a logical standby database role:

SQL> ALTER DATABASE PREPARE TO SWITCHOVER 2 TO LOGICAL STANDBY;

This statement notifies the current primary database that it will soon switch to the logical standby role and begin receiving redo data from a new primary database.




On the original logical standby database:3. Prepare the logical standby database for

switchover:SQL> ALTER DATABASE PREPARE TO SWITCHOVER

2 TO PRIMARY;

Performing a Switchover to a Logical Standby by Using SQL (continued)Perform step 3 on the logical standby database:

3. Issue the following statement to build a LogMiner dictionary on the logical standby database that is the target of the switchover:

SQL> ALTER DATABASE PREPARE TO SWITCHOVER TO PRIMARY;

This statement also starts log transport services on the logical standby database to begin transmitting its redo data to the current primary database and to other standby databases in the Data Guard configuration. The sites receiving redo data from this logical standby database accept the redo data, but they do not apply it.




On the original primary database:4. Verify the switchover status in V$DATABASE.5. Switch the primary database to the logical standby

database role:SQL> ALTER DATABASE COMMIT TO SWITCHOVER

2 TO LOGICAL STANDBY;

Performing a Switchover to a Logical Standby by Using SQL (continued)Perform steps 4 and 5 on the original primary database:

4. Verify that the LogMiner dictionary was received by the primary database by querying the SWITCHOVER_STATUS column of V$DATABASE on the primary database. When the query returns TO LOGICAL STANDBY in the SWITCHOVER_STATUScolumn, proceed with step 5.

5. Issue the following SQL statement to transition the primary database to a logical standby database role:

SQL> ALTER DATABASE COMMIT TO SWITCHOVER 2 TO LOGICAL STANDBY;

This statement waits for all current transactions on the primary database to end and prevents any new users from starting new transactions. It also puts a marker in the redo data to provide a synchronization point for logical standby database operations.Executing this statement also prevents users from making any changes to the data being maintained in the logical standby database. To ensure faster execution, ensure that the primary database is in a quiet state with no update activity before issuing the switchover statement. You can query V$TRANSACTIONS for the status of any current in-progress transactions that could delay execution of this statement.




On the new primary database (original logical standby database):6. Verify the switchover status in V$DATABASE.7. Switch the logical standby database to the primary

database role.

8. Ensure that all standby databases begin receiving redo data.

SQL> ALTER DATABASE COMMIT TO SWITCHOVER 2 TO PRIMARY;


Performing a Switchover to a Logical Standby by Using SQL (continued)Perform steps 6, 7, and 8 on the new primary database (original logical standby database):

6. Verify that the switchover notification was processed by the target standby database by querying the SWITCHOVER_STATUS column of the V$DATABASE fixed view on the target standby database. The SWITCHOVER_STATUS value is updated to show progress during the switchover. When the status is TO PRIMARY, proceed with step 7.

7. Issue the following SQL statement to switch the logical standby database to the primary role:


8. Issue the following statement to perform a log switch and to ensure that all logical standby databases begin receiving redo data from the new primary database:





On the new logical standby database:9. Start SQL Apply.SQL> ALTER DATABASE

2 START LOGICAL STANDBY APPLY;

Performing a Switchover to a Logical Standby by Using SQL (continued)Perform step 9 on the new logical standby database:

9. Issue the following statement to start SQL Apply:SQL> ALTER DATABASE START LOGICAL STANDBY APPLY;



Considerations When Performing a Switchover to a Logical Standby Database

• Switchover operation does not cause a shutdown of the primary.

• There is no need to terminate user sessions, but termination is recommended.

• Logical standby database may not have all data.• If you do switch over to a logical standby, all

physical standbys are permanently disabled.

Considerations When Performing a Switchover to a Logical Standby DatabaseConsider the following when performing a switchover to a logical standby database:

• Unlike a switchover to a physical standby database, a switchover to a logical standby database does note require a shutdown of the primary database.

• If you are switching over to a logical standby database, you do not need to terminate applications that are connected to the current primary database or to the logical standby database, because neither database is shut down during the switchover operation. However, because sessions on the old primary database may fail after the switchover operation completes and the database guard is turned on, you should terminate such open sessions now. The database guard prevents users from making changes in the logical standby database.

• If you switch over to a logical standby database, there may be a loss of data if the logical standby database contains only a subset of the data that is present in the primary database.


Considerations When Performing a Switchover to a Logical Standby Database (continued)

• When you perform a switchover to a logical standby database, any physical standby databases in the configuration are permanently disabled after the switchover and are no longer usable. The physical standby databases must be re-created from a copy of the new primary database to continue to participate in the Data Guard configuration after the role transition.



Situations That Prevent a Switchover

You cannot perform a switchover In the following situations:• Archived redo log files are unavailable.• Point-in-time recovery is required.• Production database is not open and cannot be

opened.

Situations That Prevent a Switchover The following situations prevent the execution of a switchover operation:

• Archived redo log files are unavailable: If there is a gap in the archived redo log files on the standby database, you are not able to switch over to that standby database.

• Point-in-time recovery is required: When you perform a switchover to a standby database, you always switch over to the current state of the primary database. You cannot switch over to a time in the past.

• Production database is not open and cannot be opened: A switchover is initiated on the primary database while it is in the open state. If you cannot open the primary database, a switchover is not possible.



Failover

Standbydatabase becomes primary database.


Online redologs

Local archiving

San FranciscoBoston

Archived redologs

Application

Online RedoLogs

Local Archiving

Archived redologs

Primary database

FailoverYou invoke a failover operation when a catastrophic failure occurs on the primary database and there is no possibility of recovering the primary database in a timely manner. During a failover operation, the primary database is removed from the Data Guard environment and a standby database assumes the primary database role. Failing over to a standby database is a permanent operation. You cannot undo the failover and return the database to its former role as a standby database. Because of this, you should invoke a failover operation only in an emergency.It is not always necessary to fail over to the standby database. In some cases, recovery of the primary database may be faster. Most failures can be resolved at a primary database within a reasonable amount of time.In a failover operation:

• The original primary database is presumed to be lost. You must re-create (or flash back) the original primary database as a new standby database, if desired.

• Standby databases that are online at the time of the failover operation, but are not involved in the role transition, do not need to be shut down and restarted.



Failover Considerations

• Old primary database is no longer part of the configuration.

• Data loss is possible.• Failover should be used only in an emergency.• Special-case failover: activation of a standby

Failover ConsiderationsDuring a failover operation, a standby database transitions to the primary role and the old primary database is rendered unable to participate in the configuration. Depending on the protection mode under which the old primary database was operating before the failover, there may be no or some data loss during a failover. A failover is typically used only when a primary database becomes incapacitated and there is no possibility of performing a switchover or successfully repairing the primary database within a reasonable amount of time. The specific actions that are performed during a failover vary depending on whether a logical or physical standby database is involved in the failover operation, the state of the configuration at the time of the failover, and the specific SQL commands that are used to initiate the failover.There is also a special-case failover in which the standby database is activated. This should be avoided unless absolutely necessary because it causes all other databases in the configuration to become permanently disabled.



Performing a Failover with Enterprise Manager

Select the database and click Failover.

Performing a Failover with Enterprise ManagerYou should perform a failover only in the event of a software or system failure that results in the loss of the primary database. The failed primary database is disabled by the broker and must be re-created. The standby database then assumes the primary database role.To initiate a failover by using Enterprise Manager:

1. On the Data Guard page, select the standby database that you want to become the primary database.

2. Click Failover.




Select the failover type and click Yes.

Performing a Failover with Enterprise Manager (continued)3. On the Data Guard Failover Confirmation page, you must specify the type of failover

that you want to perform:- Complete: All available redo is applied on the standby database. Oracle

Corporation recommends that you specify this type of failover.- Immediate: No additional data is applied on the standby database. This is the

fastest type of failover.4. Select the failover option, and then click Yes to confirm the failover operation.




Performing a Failover with Enterprise Manager (continued)After you click Yes, the Failover Progress page shows you the progress of the failover operation. You cannot cancel this operation after it begins.



Performing a Failover to a Physical Standby Database

The physical standby database is disabled.

Performing a Failover to a Physical Standby DatabaseDuring the failover operation, the selected standby database transitions into the primary role. If the failover target is a physical standby database, it is restarted. If you are failing over to a logical standby database, it is not restarted. When the operation is completed, the Data Guard Overview page reflects the updated configuration.Note: After a complete or immediate failover, the primary database and some standby databases may need to be re-created.



Performing a Failover to a Logical Standby Database

The logical standby database is now the primary database.

The physical standby database is disabled.

Performing a Failover to a Logical Standby DatabaseWhen you perform a failover to a logical standby database, any physical standby databases in the configuration are permanently disabled after the failover and are longer usable. These databases must be re-created from the new primary database.



Performing a Failover to a Physical Standby Database by Using SQL

1. Identify and resolve any gaps in the archived redo log files.

2. Repeat step 1 until all gaps are resolved.3. Copy any other missing archived redo log files.4. Initiate the failover operation on the target standby

database.5. Convert the physical standby database to the

primary role.6. Shut down and restart the new primary database.7. (Optional) Back up the new primary database. 8. (Optional) Restore the failed primary database.

Performing a Failover to a Physical Standby Database by Using SQL Perform the following steps to fail over to a physical standby database by using SQL.Note: If the target standby database was operating in maximum protection mode, no gaps in the archived redo log files should exist, and you can proceed directly to step 4. Otherwise, begin with step 1 to determine if any manual gap resolution steps must be performed.

1. To determine if there are gaps in the archived redo log files on the target standby database, query the V$ARCHIVE_GAP view. This view contains the sequence numbers of the archived redo log files that are known to be missing for each thread. The data returned reflects the highest gap only.

SQL> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# 2 FROM V$ARCHIVE_GAP;

If possible, copy all of the identified missing archived redo log files to the target standby database from the primary database and register them. Execute the following command to register the redo log files:

SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'filespec1';Perform this step for each thread.

2. Repeat step 1 until all gaps are resolved. The query that is executed in step 1 displays information for the highest gap only. Repeat step 1 until the query returns no rows.


Performing a Failover to a Physical Standby Database by Using SQL (continued)

3. To determine if there are any other missing archived redo log files, query the V$ARCHIVED_LOG view on the target standby database to obtain the highest sequence number for each thread.

SQL> SELECT UNIQUE THREAD# AS THREAD, MAX(SEQUENCE#)2 OVER (PARTITION BY thread#) 3 AS LAST from V$ARCHIVED_LOG;

Copy to the target standby database any available primary database archived redo log files that contain sequence numbers higher than the highest sequence number that is available on the target standby database. Then register those redo log files by issuing the following SQL statement:

SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'filespec1';

Perform this step for each thread.After registering all available archived redo log files, query the V$ARCHIVE_GAPview (as described in step 1) to verify that no additional gaps were introduced in step 3.

4. If the target physical standby database has standby redo log files configured, execute the following SQL statement to initiate the failover:

SQL> ALTER DATABASE RECOVER 2 MANAGED STANDBY DATABASE FINISH;

If the target physical standby database does not have standby redo log files configured, include the FINISH SKIP STANDBY LOGFILE clause as follows:

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE 2 FINISH SKIP STANDBY LOGFILE;

5. Transition the physical standby database to the primary database role by issuing the following SQL statement:


After issuing this SQL statement, you can no longer use this database as a standby database. Any subsequent redo that is received from the original primary database cannot be applied. During the failover process, the standby redo log files are automatically archived and recovered on all other standby databases that are derived from the original primary database if the standby destinations are correctly defined on the new primary database.

Perform step 6 on the new primary database.6. To complete the failover, you need to shut down the new primary database and restart

it in read/write mode using the initialization parameter file or server parameter file for the primary role:

SQL> SHUTDOWN IMMEDIATE;SQL> STARTUP;

7. Perform an open backup of the database after issuing the STARTUP statement. Although performing a backup immediately is not required, it is recommended because you cannot recover changes that are made after the failover without a complete backup copy of the database.


Performing a Failover to a Physical Standby Database by Using SQL (continued)

8. After a failover, the original primary database no longer participates in the configuration. After performing a failover, you may be able to optionally restore the failed primary database as a new standby database using either of the following methods:

- Use Flashback Database to restore the failed primary database to a point in time before the failover occurred, and then convert it into a standby database

- Re-create the failed database and add it to the configuration as a new standby database. To reuse the old primary database in the new configuration, you must re-create it as a standby database using a backup copy of the new primary database.

After the failed primary database is restored and is operating in the standby role, you can optionally perform a switchover to transition the databases to their original (pre-failure) roles.



Performing a Failover to aLogical Standby Database by Using SQL

1. Copy redo logs to the logical standby database.2. Register the missing redo logs:

3. If it exists, register the partially filled archive log file.

4. Ensure that all redo log files have been applied to the new primary database.

SQL> ALTER DATABASE REGISTER LOGICAL 2 LOGFILE 'filespec';

Performing a Failover to a Logical Standby Database by Using SQLTo perform failover for logical standby databases using SQL:

1. If redo logs exist on the primary database that have not yet been applied on the logical standby database, manually copy the redo logs to that standby database.

2. You must register the redo log files that you manually copied from the original primary database. Issue the following SQL statement for each missing redo log file on the logical standby:

SQL> ALTER DATABASE REGISTER LOGICAL LOGFILE 'filespec';

3. On the logical standby database, check to see if there is a partially written archived log file. If it exists, this file has a sequence number that is one greater than the last registered archived log file. If it exists, register the partially filled archived log file.

4. On the new primary database, ensure that the remaining redo logs have been applied by checking the DBA_LOGSTDBY_PROGRESS view. When the values in the APPLIED_SCN and NEWEST_SCN columns are equal, all available redo has been applied. The logical standby database now contains as much data as possible from the primary database. Issue the following query:




Performing a Failover to aLogical Standby Database by Using SQL

5. Activate the new primary database:

6. Enable archiving of redo logs.7. Begin SQL Apply operations on all logical standby

databases:

SQL> ALTER DATABASE STOP 2 LOGICAL STANDBY APPLY;

SQL> ALTER DATABASE ACTIVATE 2 LOGICAL STANDBY DATABASE;

SQL> ALTER DATABASE START LOGICAL STANDBY 2 APPLY NEW PRIMARY dblink;

Performing a Failover to a Logical Standby Database by Using SQL (continued)5. To stop SQL Apply operations and activate the database in the primary database role,

issue the following statements on the logical standby database that you are transitioning to the new primary role:

SQL> ALTER DATABASE STOP LOGICAL STANDBY APPLY;SQL> ALTER DATABASE ACTIVATE LOGICAL STANDBY DATABASE;

6. Enable archiving of redo logs to all remote logical standby destinations, as in the following example:

SQL> ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;In general, when the database operates in the primary role, you must enable archiving of redo logs to remote destinations. When the database operates in the standby role, you must disable archiving of redo logs to remote destinations..

7. Issue the following command to begin SQL Apply operations on all logical standby databases in the configuration:

SQL> ALTER DATABASE START LOGICAL STANDBY 2 APPLY NEW PRIMARY dblink;

Note: Any logical standby databases that are more current (have applied more redo operations) than the standby database to which the primary database has failed over to must be re-created from a backup of the new primary database and added back to the configuration.



Activating a Standby Database

When you are unable to fail over, you can activate a standby database by issuing one of the following commands (depending on the role of the database):

SQL> ALTER DATABASE ACTIVATE 2 LOGICAL STANDBY DATABASE;

SQL> ALTER DATABASE ACTIVATE 2 PHYSICAL STANDBY DATABASE;

Activating a Standby DatabaseYou can use the ALTER DATABASE ACTIVATE STANDBY DATABASE command to force the standby database into the primary role. Specify the appropriate option, PHYSICAL or LOGICAL, for the type of database that you are activating. You can issue this command in a situation in which you cannot perform a failover operation.Note: You cannot perform an activation operation to a physical standby database on which standby redo logs are present unless you indicate that it is acceptable to skip applying the contents of the standby redo log with the FINISH SKIP STANDBY LOGFILE keywords on the RECOVER MANAGED STANDBY DATABASE statement.



Using Flashback Database After Failover

Failover

New standby database

Redo

RedoNew primary database

Flashback

Primary database

Standby database

Using Flashback Database After FailoverYou invoke a failover operation when a catastrophic failure occurs on the primary database and there is no possibility of recovering the primary database in a timely manner. After a failover operation, the old standby database becomes the new primary database, and the old primary database is removed from the Data Guard configuration. You can use the Flashback Database feature to convert the old primary database into a new standby database without re-creating the database. You can flash back the old primary database so that it contains only those changes that are already applied to the old standby database. This enables you to convert the old primary database into a new standby database without restoring the old primary database.Note: You must have the Flashback Database feature enabled on the old primary database.


Using Flashback Database After Failover (continued)Physical Standby ConfigurationIn a physical standby configuration, use the following procedure to avoid reinstantiating the old primary database after a failover:

1. On the new primary database, issue the following query to determine the system change number (SCN) at which the old standby database became the new primary database:

SELECT standby_became_primary_scn FROM v$database;

2. After the old primary database site is available, mount the old primary database.3. Flash back the old primary database to the “standby became primary” SCN that you

determined in step 1:FLASHBACK DATABASE TO SCN <SCN>;

4. Disable Flashback Database on the old primary database by issuing the following command:

ALTER DATABASE FLASHBACK OFF;

5. On the old primary database, create a new standby database control file.6. Shut down the old primary instance.7. On the old primary database, replace the existing control file with the new standby

control file.8. Mount the old primary database. The old primary database is now your new standby

database. Also verify that the listener is running:STARTUP MOUNT;lsnrctl status listener_name

9. On the new standby, enable Flashback Database:ALTER DATABASE FLASHBACK ON;

10. On the new primary database, enable log transport to the old primary (new standby). Check the status of the archive destinations and enable any that are not enabled. Then archive a new log to the new standby by issuing the following command:

SELECT DEST_ID, DEST_NAME, STATUS, PROTECTION_MODE, DESTINATION, ERROR, SRL FROM V$ARCHIVE_DEST_STATUS;ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_n=ENABLE;ALTER SYSTEM ARCHIVE LOG CURRENT;

11. On the new standby, start managed standby recovery. The role reversal is now complete:

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;

If you are using real-time apply:ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;


Using Flashback Database After Failover (continued)Logical Standby ConfigurationIn a logical standby configuration, use the following procedure to avoid reinstantiating the old primary database after a failover:

1. On the new primary database, issue the following query to determine the SCN at which the old standby database became the new primary database:

SELECT value AS standby_became_primary_scn FROM dba_logstdby_parametersWHERE name = 'END_PRIMARY_SCN';

2. After the old primary database site is available, mount the old primary database.3. Flash back the old primary database to the “standby became primary” SCN that you

determined in step 1:FLASHBACK DATABASE TO SCN <SCN>;

4. Enable the Data Guard guard to prevent the job queue from executing:ALTER DATABASE GUARD ALL;

5. Open the database with the RESETLOGS option: ALTER DATABASE OPEN RESETLOGS;

6. Create a database link to the new primary database, and then start SQL Apply:CREATE PUBLIC DATABASE LINK mylink CONNECT TO systemIDENTIFIED BY password USING 'service_name_of_new_primary_database';ALTER DATABASE START LOGICAL STANDBY APPLY NEW PRIMARY mylink;



Summary

In this lesson, you should have learned how to:• Use the Data Guard GUI to perform switchover and

failover operations• Use SQL commands to perform switchover and

failover operations• Use Flashback Database after a failover




This practice covers the following topics:• Performing a switchover• Performing a failover


Using Data Guard with RAC



Objectives

After completing this lesson, you should be able to deploy Data Guard in a Real Application Clusters environment.



Real Application Clusters and Data Guard

Possible combinations of instances in the primary and standby databases:

YesYesMulti-Instance

YesYesSingle-Instance

Multi-InstanceStandby Database

Single-InstanceStandby Database

PrimaryInstance

Real Application Clusters and Data GuardYou can configure your Real Application Clusters (RAC) environment to switch over to another RAC environment or a single-instance environment. If you configure switchover to another RAC environment, each node in the RAC ships its redo information to a corresponding RAC node. The shipping and receiving of the redo information are spread across the nodes of the RAC. The apply services are performed on one node in the RAC. After switchover or failover, your application is in a RAC, which should give the same performance as the previous configuration.If you configure switchover to a single instance, performance can be impeded because one system has to receive and apply all logs from all members of the RAC. Also, switchover and failover to a smaller system do not allow your application to perform as in the original configuration. If you are sending redo to a single-instance standby, be sure to configure the number of standby redo logs on the standby database to be equal to the total number of online redo logs in all the instances of the RAC system.



Configuration Considerations with RAC

• Format for archived redo log file names: Thread variable (%t or %T) of LOG_ARCHIVE_FORMAT is mandatory.

• Archive destination quotas: Use the QUOTA_SIZEattribute of the LOG_ARCHIVE_DEST_n parameter.

• Data protection modes: Maximum protection or maximum availability mode; all instances could stop shipping redo.

Configuration Considerations with RACFormat for archived redo log file names: The thread variable (%t or %T) in the LOG_ARCHIVE_FORMAT parameter is mandatory for Real Application Clusters to uniquely identify the archived redo log files.Archive destination quotas: You can specify the amount of physical storage on a disk device to be available for an archiving destination using the QUOTA_SIZE attribute of the LOG_ARCHIVE_ DEST_n initialization parameter. An archive destination can be designated as being able to occupy all or some portion of the physical disk that is represented by the destination. For example, a physical disk device can be shared by two or more separate nodes in a Real Application Clusters environment. Because there is no cross-instance initialization parameter knowledge, none of the Real Application Clusters nodes are aware that the physical disk device is shared with other instances. This leads to substantial problems when the destination disk device becomes full; the error is not detected until every instance tries to archive to the already-full device. This affects database availability.


Configuration Considerations with RAC (continued)Data protection modes: In a RAC configuration that is configured for maximum protectionor maximum availability mode, any instance that loses connectivity with a standby destination causes all other instances to stop sending data to that destination. This action maintains the data integrity of the data that has been transmitted to that destination and can be recovered. When the failed standby destination comes back up, Data Guard runs the site in resynchronization mode until no gaps remain. Then, the standby destination can participate in the Data Guard configuration again.



Multi-Instance Primary with a Single-Instance Standby

Multi-Instance Primary with a Single-Instance StandbyYou can create a single-instance standby database by using either SQL commands or Enterprise Manager. Each instance of the primary database sends redo to the one instance of the standby. The standby database automatically determines the correct order in which to apply the archived redo log files.



Multi-Instance Primary with a Multi-Instance Standby

Multi-Instance Primary with a Multi-Instance StandbyAlthough the Add Standby Database Wizard does not create a RAC standby database, you can use it to add an existing RAC standby database to a Data Guard configuration. Click Add Standby Database to invoke the Add Standby Database Wizard, and then select “Add an existing standby database.”The Data Guard broker also has the ability to dynamically discover instances of a database and add them to a database profile without user intervention. After they are added, the broker can manage these instances when it comes to conducting state changes, role changes, and so on. If a new primary instance is added, the broker automatically enables the log transport service on that instance and gets that instance to ship its redo to the configured set of standbys. During role changes and protection mode upgrades, the broker also manages the instance restarts because it is integrated with the RAC Cluster Ready Services (CRS).



Log Transport with RAC to RAC

Primary instance A

Primary instance B

Standby instance C

Standby recovery instance D

Archived logs

Archived logs

Onlineredofiles

Standbyredofiles

Archivedlogs

LGWR RFS ARCn

LGWR

Primary database


MRP

Log Transport with RAC to RAC The best practice is to send all redo to the recovery instance on the standby RAC. When both the primary and standby databases are in a Real Application Clusters configuration, then a single instance of the standby database applies all sets of log files that are transmitted by the primary instances. In this case, the standby instances that are not applying redo data cannot be in read-only mode while Redo Apply is in progress.



Setting Up a Primary Database with RAC

Primary instance A

Primary instance B

Archived logs

Archived logs

Onlineredofiles

LGWR

LGWR

Primary database

Setting Up a Primary Database with RACTo configure log transport services on the primary database:

1. On all instances, define the LGWR attribute for the LOG_ARCHIVE_DEST_nparameter to specify that the LGWR process performs the archival operation.

2. Configure each standby instance to send redo data to the recovery instance by setting the LOG_ARCHIVE_DEST_n parameter to an appropriate value.



Setting Up a Standby Database with RAC

Standby instance C

Standby recovery instance D

Standbyredofiles

Archivedlogs

RFS ARCn


MRP

Setting Up a Standby Database with RACTo configure log transport services on the standby database:

1. Create the standby redo log files. In a Real Application Clusters environment, the standby redo log files must reside on disk devices that are shared by all instances.

2. On the recovery instance, define the LOCATION attribute of the LOG_ARCHIVE_DEST_1 initialization parameter to archive locally.

3. Start log apply services on the recovery instance.



Assigning Threads to Standby Redo Log Groups

SQL> ALTER DATABASE ADD STANDBY LOGFILE2 THREAD 1 'STBY_LOGFILE_1.SRL' SIZE 50M;

Primarydatabase

Standbydatabase

Standby redo logs

Assigning Threads to Standby Redo Log GroupsUse the THREAD n clause in the ALTER DATABASE ADD STANDBY LOGFILE statement to assign a standby redo log group to a specific thread. With this clause, you can balance the use of standby redo log groups across all threads. The THREAD n syntax is optional. If the syntax is omitted, Data Guard automatically assigns the standby redo log to a thread at run time. This is applicable only if you are using the RAC. Because standby redo log groups are now assigned to a given thread, you may need more standby redo log groups. This is because there is no longer a pool of files available for any thread. If you have threads that generate more redo then others, assign more standby redo log groups to that thread. It is usually sufficient to assign one or two more than there are online log files.



Apply Instance Failover• If the apply instance fails, transport of redo is also

halted by default. • Broker configuration:

– Set ApplyInstanceTimeout to avoid down time.– Default is 120 seconds.– Set to 0 (zero) to disable.

– Optionally set PreferredApplyInstance.• Non-broker configuration: Set up a list of

destination connect identifiers.

Apply Instance FailoverWhen the apply instance fails, not only does log apply services stop applying log files to the standby database, but log transport services stop transmitting redo data to the standby database. To tolerate a failure of the apply instance, the broker leverages the availability of the RAC standby database by automatically failing over log apply services to a different standby instance. To set up apply instance failover in a Data Guard broker–controlled configuration, set theApplyInstanceTimeout property to specify the time period that the broker should waitafter detecting an apply instance failure and before initiating an apply instance failover. To select an appropriate timeout value, you must consider:

• If there is another mechanism in the cluster that will try to recover the failed apply instance

• How long the primary database can tolerate not transmitting redo data to the standby database

• The overhead that is associated with moving the log apply services to a different instance. The overhead may include retransmitting (from the primary database) all log files that have accumulated on the failed apply instance that have not been applied if those log files are not saved in a shared file system that can be accessed from other standby instances.


Apply Instance Failover (continued)You can also set the the PreferredApplyInstance property of Data Guard broker to indicate which instance should take over this task if the current apply instance fails. If PreferredApplyInstance is not set, the broker picks a random instance that is currently running to be the new apply instance. If the Data Guard broker is not enabled for your configuration, Oracle’s high availability best practices recommend setting up a list of destination connect identifiers in the tnsnames.ora file on the primary, as in the following example:

CHICAGO=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=chicago_n1-server)(PORT=1521))(ADDRESS=(PROTOCOL=tcp)(HOST=chicago_n2-server)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=CHICAGO)))

In this case, LGWR chooses the next entry in the list to send redo data to, after a timeout period that is specified in the NET_TIMEOUT attribute of the log_archive_dest_nparameter (if NET_TIMEOUT is not specified, it waits until the system’s TCP/IP timeout). However, the apply process (Redo Apply or SQL Apply) would need to be manually started in the new instance with SQL*Plus.The primary instance of the standby cluster will be brought down to ensure no data loss if all of the following are true:

• A connection list is not specified.• The Data Guard broker is not enabled for the configuration.• The apply instance for the last standby fails.• The LGWR process times out.



Role Transitions with RAC

• Switchovers: Only one primary instance and one standby instance can be active during a switchover.

• Failovers: Before performing a failover to a RAC standby database, you should shut down all but one standby instance.

Role Transitions with RAC Switchovers: For a RAC database, only one primary instance and one standby instance can be active during a switchover. Before a switchover, therefore, you should shut down all but one primary instance and one standby instance. After the switchover completes, restart the primary and standby instances that you shut down during the switchover.Note: The ALTER DATABASE statement that is used to perform the switchover automatically creates redo log files if they do not already exist. Because this can significantly increase the time that is required to complete the COMMIT operation, Oracle Corporation recommends that you always manually add redo log files when configuring raw devices for physical standby databases.

Failovers: Before performing a failover to a RAC standby database, shut down all but one standby instance. After the failover completes, restart the instances that were shut down.



Troubleshooting

• Switchover failure • Avoiding down time during a network outage

TroubleshootingSwitchover failure: When your database is using RAC, active instances prevent a switchover from being performed. When other instances are active, an attempt to switch over fails and the following error message appears:

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY;ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY *ORA-01105: mount is incompatible with mounts by other instancesQuery the GV$INSTANCE view to determine which instances are causing the problem:SQL> SELECT INSTANCE_NAME, HOST_NAME FROM GV$INSTANCE

2 WHERE INST_ID <> 3 (SELECT INSTANCE_NUMBER FROM V$INSTANCE);

INSTANCE_NAME HOST_NAME------------- ---------INST2 standby2

Connect to this instance and shut it down.


Troubleshooting (continued)Avoiding down time: If you configured Data Guard to support a primary database in a RAC environment and the primary database is running in maximum protection mode, a network outage between the primary database and all of its standby databases will disable the primary database until the network connection is restored. The maximum protection mode dictates that if the last participating standby database becomes unavailable, processing halts on the primary database.If you expect the network to be down for an extended period of time, consider changing the primary database to operate in either maximum availability or maximum performance mode until network connectivity is restored. If you change the primary database to maximum availability mode, it is possible for there to be a lag between the primary and standby databases, but you gain the ability to use the primary database until the network problem is resolved.If you choose to change the primary database to maximum availability mode, it is important to use the following procedures to prevent damage to your data.The following steps describe what to do if the network goes down and you want to change the protection mode for the RAC configuration. The example assumes that you are using a server parameter file (SPFILE) rather than a text initialization parameter file (PFILE).

1. At this point, all RAC primary instances are shut down. Issue the STARTUP MOUNTcommand to start one instance:STARTUP MOUNT;

2. Change the mode from maximum protection to either maximum availability or maximum performance. For example, the following statement sets the maximum availability protection mode:

ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVAILABILITY;

3. Open the RAC primary database for general access. When the network comes back up later, perform the following steps to revert to maximum protection mode:

1. Shut down all instances of the RAC primary database.2. Mount a single instance of the RAC primary database without opening it for general

access.3. Change the mode on the RAC primary database from its current mode (maximum

availability or maximum performance) to maximum protection mode.4. Open the RAC primary database for general access.



Summary

In this lesson, you should have learned how todeploy Data Guard in a Real Application Clusters environment.


Other Considerations for Oracle Data Guard



Objectives

After completing this lesson, you should be able to do the following:• Back up the primary database with a physical

standby database • Back up a logical standby database • Use Flashback Database features in a Data Guard

configuration • Encrypt redo information • Configure cascaded redo log destinations



Offloading Backups to a Physical Standby

• Backups of data files and archived redo logs are fully interchangeable.

• Control file backups are not interchangeable.• Primary and standby databases must use the

same recovery catalog.• It is not necessary to register the standby

database.

Offloading Backups to a Physical StandbyRecovery Manager (RMAN) can back up the standby database and its associated archived redo logs. Standby backups of data files and archived redo logs are fully interchangeable with primary database backups. In other words, you can execute the RESTORE command to restore a backup of a standby data file to the primary database, and you can restore a backup of a primary data file to the standby database. The standby control file and primary control file, however, are not interchangeable.Both the primary database and standby database must use the same recovery catalog. Note that you do not need to register the standby database in the catalog if the primary is already registered; simply connect to the standby database and execute the BACKUP command.



Backing Up a Physical Standby Database with RMAN

1. Invoke RMAN.2. Allocate channels if needed.3. Issue the BACKUP command.4. Use the LIST command to verify the backup.

Backing Up a Physical Standby Database with RMANUse the RMAN BACKUP command to back up the standby database. Performing a backup on the standby database is exactly the same as a backup of the primary database, except that the backup takes place on the standby site.



Restrictions and Usage Notes

• The database you are backing up must be a physical standby database.

• You must be connected to the recovery catalog when backing up.

• You cannot back up the standby control file.• You must connect to the physical standby

database with the TARGET keyword.

Restrictions and Usage NotesIf physical standby database backups are to be usable for restore jobs at the primary site, you must be connected to the recovery catalog when backing up the standby database or must resynchronize the physical standby database shortly after the backup. This step is necessary because there is no way for the primary database to know about the standby backups unless the backup records are stored in the recovery catalog. You cannot back up the standby control file. Also, you cannot make an image copy or non-RMAN backup of the standby control file and then use it to restore the primary database. When you back up the standby database, you must connect to the standby database with the TARGET keyword (not the AUXILIARY keyword). Essentially, the standby database is “substituting” for the primary database during the backup.



Backup and Recovery of aLogical Standby Database

• Backup considerations: – Use same backup method you use for your primary

database.– Files are not interchangeable with primary

database.• Recovery considerations:

– Can recover like any other database for loss of individual files

– Need to re-create if you lose entire database– Must use a binary copy of control file for control file

recovery

Backup and Recovery of a Logical Standby DatabaseYou can back up your logical standby database by using the same method that you use for your primary database. The backup files are not interchangeable with the primary database. Remember that this is a different database.You can use the same recovery techniques as with any other database for loss of data files or online log files. You must use the backups of the logical (not the primary) database. If the entire logical standby database is lost, you must re-create the logical standby. If you lose all copies of your control file, you must use a binary copy of the control file when performing the recovery. Using a trace file or the CREATE CONTROLFILEcommand for control file recovery does not create a logical standby control file. You can make a binary copy of the control file by doing either of the following:

• Shut down the logical standby and copy the control file to a backup. • Issue the following command while the logical standby database is open:

ALTER DATABASE BACKUP CONTROLFILE TO '<filename>';

This command creates a binary copy of the control file with the name that you supply.



Using Flashback Database and Real-Time Apply

RFS

Standbyredo log

MRP

ARC0

Archivedredo logs

Primary database

Standby database

Using Flashback Database and Real-Time ApplyYou can reduce failover time by using the Oracle Data Guard real-time apply feature. You can protect a physical standby database from logical data corruption or user error by using Flashback Database.



Using Flashback Database After RESETLOGS

Redo

Redo

Flashback

Primary database

Standby database

RESETLOGSafter

point-in-timerecovery

Primary database Standby database

Using Flashback Database After RESETLOGSPhysical Standby ConfigurationUse the following procedure to avoid re-creating a standby database after you have performed an OPEN RESETLOGS on the primary database and the managed recovery process has halted on the physical standby database:

1. On the primary database, determine an SCN that is at least two SCNs prior to the SCN when the OPEN RESETLOGS command was issued. This is necessary to enable the standby to recover properly through the OPEN RESETLOGS. Use the following query to find the “before RESETLOGS” SCN:

SELECT TO_CHAR(resetlogs_change# - 2) FROM v$database;

2. On the standby database, obtain the current SCN by using the following query: SELECT TO_CHAR(current_scn) FROM v$database;


Using Flashback Database After RESETLOGS (continued)3. Flash back the standby database to the “before RESETLOGS” SCN that you queried in

step 1: FLASHBACK STANDBY DATABASE TO SCN <before RESETLOGS SCN>;

4. Restart managed recovery on the standby database. The standby database should now be ready to receive and apply logs from the primary database:

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;

Logical Standby ConfigurationFor a logical standby database, it is possible that the SQL Apply service might not halt when it encounters the OPEN RESETLOGS command in the redo information. If the logical standby database’s SCN is far enough behind the primary database’s SCN, then the SQL Apply service will be able to interpret the OPEN RESETLOGS command without stopping.Use the following procedure to avoid re-creating a standby database after you have performed an OPEN RESETLOGS on the primary database and the SQL Apply process has halted on the logical standby database:

1. On the primary database, determine an SCN that is at least two SCNs prior to the SCN when the OPEN RESETLOGS command was issued. This is necessary to enable the standby to recover properly through the OPEN RESETLOGS. Use the following query to find the “before RESETLOGS” SCN:

SELECT TO_CHAR(resetlogs_change# - 2) FROM v$database;

2. On the standby database, obtain the current SCN with the following query: SELECT TO_CHAR(current_scn) FROM v$database;

3. Flash back the standby database to the “before RESETLOGS” SCN that you queried in step 1:

FLASHBACK STANDBY DATABASE TO SCN <before RESETLOGS SCN>;

4. Restart SQL Apply on the standby database. The standby database should now be ready to receive and apply logs from the primary database:

ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE;



Enabling Redo Encryption

Primarydatabase

Standbydatabase

Redo information encrypted

Enabling Redo EncryptionYou can optionally enable encryption of the redo data by using the following procedure:

1. Install the Oracle Advanced Security option at both the primary and standby database.2. Configure the appropriate SQLNET.ORA parameters to enable Oracle Net to encrypt

the redo traffic shipped to the standby. An outline of the tasks to configure encryption on the client and on the server using Oracle Net Manager is as follows:

a. Navigate to the Oracle Advanced Security profile.b. Choose the Encryption tab.c. Select CLIENT or SERVER from the list.d. From the Encryption Type list, select one of the following: REQUESTED,

REQUIRED, ACCEPTED, or REJECTED. e. (Optional) In the Encryption Seed field, enter between 10 and 70 random

characters; the encryption seed for the client should not be the same as that for the server.

f. Choose File > Save Network Configuration. The SQLNET.ORA file is updated.g. Repeat this procedure to configure encryption on the other system.

Refer to the Oracle Database Advanced Security Administrator's Guide for detailed information.



Cascaded Redo Log Destinations

Primarydatabase Standby

database

Standbydatabase

Redo

Redo

Cascading Redo Log DestinationsTo reduce the load on your primary system, you can implement cascaded redo log destinations, whereby a standby database receives its redo data from another standby database instead of directly from the primary database. You can configure:

• A physical standby database to retransmit the incoming redo data that it receives from the primary database to other remote destinations in the same manner as the primary database

• A logical standby database (because it is open in read/write mode) to send the redo data that it generates (after filtering and applying the redo data that it receives from the primary database) to its own set of standby (physical or logical) databases

Note: You must use SQL commands when managing a cascaded redo log destination configuration because Data Guard broker does not support this feature.



Configuring Cascaded Redo Log Destinations: Physical Standby

• On the primary, use the LGWR transport.• On receiving a standby, configure standby redo

logs.• On receiving a standby, configure

LOG_ARCHIVE_DEST_n to send redo to the next standby.

Physicalstandby

Primarydatabase

Physical orlogical standby

Configuring Cascaded Redo Log Destinations: Physical StandbyTo enable a physical standby database to send the incoming redo data to another set of destinations, you must do the following:

• Define the LOG_ARCHIVE_DEST_n initialization parameter on the primary database to set up a physical standby database as the starting point for a cascade to use the LGWR transport method. Use either SYNC or ASYNC network protocols, depending on your requirements.

• On the receiving physical standby database, define sufficient standby redo log files and ensure that archiving is enabled.

• Define the LOG_ARCHIVE_DEST_n initialization parameter on the physical standby database that will define the end points of the cascade.

Remember that, as part of the original setup of the physical standby database, you should have defined a local archive destination to be used for local archiving when the physical standby database transitions to the primary role. For example, you might define the LOG_ARCHIVE_DEST_1 initialization parameter to be the 'LOCATION=/physical1/arch' location. When the physical standby database switches roles, any archived redo log files are put into that directory with the same format that you defined with the LOG_ARCHIVE_FORMAT initialization parameter.


Configuring Cascaded Redo Log Destinations: Physical Standby (continued)This local archiving destination can be the same as the one that is defined in the parameter STANDBY_ARCHIVE_DEST, but this is not required.A side effect of this configuration is that the archiver process on the standby database now tries to send the redo data not only to the cascading end points, but also to the other standby databases and the primary database if they are defined and enabled. The shipping of redo back to the primary or another standby is not a problem, because the receiving database will reject it. If the destination is another standby database and it has not received the log file successfully, then the shipping of redo acts as an active gap resolution. You can avoid the shipping of redo to the primary and other standbys by setting the state to DEFER for any destinations not involved in the cascade. However, you must remember to enable them again if you do a switchover or failover operation.If you want to have one initialization parameter file handle both the cascaded redo log destinations and the original primary and standby destinations, define the destinations for the primary database and other standby databases as well as for the cascading standby databases. However, the total remote destinations still cannot exceed 10, including the local archiving destination.



Configuring Cascaded Redo Log Destinations: Logical Standby

• The cascading standby database is created from a backup of the logical standby database, not from the primary database.

• Set up the cascading standby just like any other standby.

Logicalstandby

Primarydatabase

Physical orlogical standby

Configuring Cascaded Redo Log Destinations: Logical Standby A logical standby database that receives redo data directly from the primary database can be configured to cascade the redo data that it generates to other standby databases (after it has filtered and applied the redo data it receives from the primary database). Because redo data that is cascaded from a logical standby database is not identical to the redo data originally generated by the primary database, it cannot be applied to any standby database that is created directly from the primary database. Instead, any standby databases that receive cascaded redo data from a logical standby database must be created from a copy of the logical standby database, and the following will be true:

• Physical standby databases that are created from a logical standby database will be a block-for-block copy of the logical standby database and a logical copy of the original primary database.

• Logical standby databases that are created from a logical standby database will be logical copies of the parent logical standby database and might bear only a partial resemblance to the original primary database. This is because the original primary database’s data is there and so is anything else that is stored in the parent logical standby database (including any other changes, such as different indexes or materialized views).


Configuring Cascaded Redo Log Destinations: Logical Standby (continued)For standby databases that receive cascaded redo data from a logical standby database, you must perform the same setup tasks as for a physical or logical standby database that receives redo data directly from the primary database. You can use any transport mode (LGWR or ARCH) and network protocol (SYNC or ASYNC). If you use the LGWR transport mode, you can optionally use standby redo log files on your standby databases.



Role Transitions withCascaded Redo Log Destinations

• Standby databases that receive redo data from a physical standby database:– No change: Switchover and failover are exactly the

same.– May take longer

• Standby databases that receive redo data from a logical standby database cannot participate in a switchover involving the primary database.

Role Transitions with Cascaded Redo Log DestinationsThe process to perform a switchover or failover is exactly the same in a cascaded redo log destinations configuration, because all physical standby databases that receive retransmitted primary database redo data are identical and valid for role transitions. The only difference is that additional time may be required for the end-of-redo data to cascade to the standby database.Any standby database that receives redo data that is cascaded from a logical standby database cannot participate in a switchover involving the primary database. (Only logical standby databases that receive redo data directly from the primary database can participate in switchovers.) If you fail over to a database that receives redo data that is generated by a logical standby database, then only other logical standby databases that receive redo data cascaded from the same logical standby database are able to continue to participate in the Data Guard configuration after the failover.



Summary

In this lesson, you should have learned how to:• Back up the primary database with a physical

standby database • Back up a logical standby database • Use Flashback Database features in a Data Guard

configuration • Encrypt redo information • Configure cascaded redo log destinations


Workshop



Objectives

After completing this lesson, you should be able to do the following:• Explain the workshop methodology• Explain the workshop setup



Workshop Premise

• You are the DBA at a growing company that has decided to implement Oracle Data Guard to protect its Oracle database.

• You use Enterprise Manager and SQL commands to manage your Data Guard configuration.



Workshop Flow

In this workshop, you perform the following tasks:• Create one or more standby databases.• Verify the configurations.• Change the protection mode.• Retrieve information from the standby database.• Perform failovers.



Workshop Scenarios

The workshop is comprised of the following scenarios:1. Create a Data Guard configuration to ensure high

availability, data protection, and disaster recovery.2. Verify the configuration and the operation of log

transport and apply services.3. Verify that the automatic gap detection and

resolution feature is working properly.4. Change the protection mode to meet stated

requirements.5. Configure the feature that enables log apply

services to apply redo data as it is received.

General Notes for the WorkshopThe scenarios should be performed in order. If you finish them and would like to run some separately, you can. Just be sure to keep track of what role each database is in before you start a scenario.



Workshop Scenarios

6. Configure the feature that will ensure you will not need to re-create the primary database after failover.

7. Add an additional data file to your primary database.

8. Configure the standby database so that users can use it for reporting.

9. Add a standby database that will support reporting.

10. Verify that the automatic gap detection and resolution feature is working properly.



Workshop Scenarios

11. Configure SQL Apply so that specified DML statements are not executed on the logical standby database.

12. Create a new view on the logical standby database.

13. Perform a failover operation.14. Enable your logical standby database after the

failover.15. Add your original primary database back into the

configuration.



Summary

In this lesson, you should have learned:• The flow of the workshop• The setup that is used for the workshop• Some hints that will help you through the

workshop


Workshop PreparationTo prepare for the workshop, you need to drop your Data Guard configuration and your standby databases. Perform the following steps:

1. Access the Data Guard page and drop your Data Guard configuration by selecting Remove Data Guard Configuration in the Additional Administration section. Click Yes on the Confirmation: Remove Data Guard Configuration page to confirm.

2. To add entries for these databases, edit the /etc/oratab file on the server machine that your standby databases are on. The entries use the instance name to reference the instance and database. This step is required so that you will be able to delete the databases using DBCA.

3. Invoke DBCA on the server machine your standby databases are on and delete your standby databases.

4. Remove your <HOSTNAME>_SITE1 and <HOSTNAME>_SITE2 databases from Grid Control.


Workshop ScenariosIn the workshop you will create standby databases and modify your configuration to meet the business requirements outlined in the workshop scenarios.

1. You need to create a Data Guard configuration to ensure high availability, data protection, and disaster recovery for your enterprise data. You want to be able to open your standby database in read-only mode so that queries can be executed. Create your standby database to meet these requirements with the following specifications:Standby database unique and target name: <YOUR_HOSTNAME>_SITE1Location: Create your standby database on the next-highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your physical standby database named EDRSR8P1_SITE1 on EDRSR8P2. If you are on EDRSR8P12, create your standby database on EDRSR8P1.

2. You want to ensure that you have created your standby database successfully and that the log transport and apply services are working. Use Enterprise Manager to confirm that your Data Guard configuration is functioning properly.

3. You understand that Data Guard can automatically detect archive gaps and resolve those gaps by copying the missing sequence of log files to the standby destination. As an example, if connectivity is lost between the primary and one or more standby databases (for example, due to network problems), redo data being generated on the primary database cannot be sent to those standby databases. Once a connection is reestablished, the missing archived redo log files (referred to as a gap) are automatically detected by Data Guard, which then automatically transmits the missing archived redo log files to the standby databases. Verify that this feature is working properly in your configuration by simulating a loss of connectivity. Disable log transport services to your standby database, switch the log on your primary database, and re-enable log transport services to your standby database.

4. Maximum performance is the default protection mode and provides the highest level of data protection that is possible without affecting the performance of the primary database. This is accomplished by allowing a transaction to commit as soon as the redo data needed to recover that transaction is written to the local online redo log. You have determined that you need to change the data protection mode to ensure the redo data needed to recover each transaction is written to both the local online redo log and to the standby redo log on at least one standby database before the transaction commits. You also want to configure the protection mode so that the primary database does not shut down if a fault prevents it from writing its redo stream to a remote standby redo log. Change the protection mode so that your configuration meets these requirements.


Workshop Scenarios (continued)

5. You want to ensure fast switchover and failover times should you need to perform those operations. Configure the Data Guard feature that enables log apply services to apply redo data as it is received, without waiting for the current standby redo log file to be archived.

6. You want to ensure that you will not need to re-create the primary database after you have performed a failover operation. Configure the feature that will enable you to flash back the failed primary database to a point in time before the failover and convert it into a standby database for the new primary database.

7. You have been asked to add an additional data file to the EXAMPLE tablespace in your primary database. Add the data file with the following specifications:Data file name: /u01/app/oracle/oradata/orcl/example02.dbfData file size: 2 MBVerify that the new data file has been added to your standby database.

8. The application users need to run some additional reports and do not want to impact the production system. Perform the steps required to make the standby database available for this reporting task. Verify that you can query tables in the standby database and then restart real-time apply so that the standby database will be resynchronized with the primary database.

9. You have determined that the users will need to run reports on a regular basis and do not want to impact the production database. In addition, you would like to add an additional standby database to your configuration for additional data protection. Configure a second standby database that will be available for users to perform queries, summations, and reporting activities against at all times with the following specifications:Standby database unique and target name: <HOSTNAME>_SITE2Location: Create your standby database on the next-highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your standby database on EDRSR8P2. If you are on EDRSR8P12, create your standby database on EDRSR8P1.

10. Verify that the automatic gap detection and resolution feature is working properly in your configuration by simulating a loss of connectivity to your new standby database. Disable log transport services to your standby database, switch the log on your primary database, and re-enable log transport services to your standby database.


Workshop Scenarios (continued)

11. Because the users want to use some tables in the new standby database to report against for historical purposes, you need to configure SQL Apply so that certain DML statements are not executed against those tables on the logical standby database. You decide to test this feature first by creating a new table on the primary database as follows:

CREATE TABLE hr.emp_name AS SELECT first_name, last_name

FROM hr.employees WHERE 1=2;

Define a filter that prevents SQL Apply from issuing DML statements against the HR.EMP_NAME table on the logical standby database. Insert a few rows into the HR.EMP_NAME table on the primary database and commit your changes. Force a log switch on the primary database and then verify that the new rows are not applied to your logical standby database.

12. You have been asked to create a view for the users to query on the logical standby database. Create the view as follows:

CREATE VIEW hr.emp_90_vw AS SELECT *

FROM hr.employees WHERE department_id=90;

13. You have experienced a failure on your primary database server. Fail over to your physical standby database.

14. Your logical standby database is disabled after the failover. Enable your logical standby database.

15. You have been able to restore the server which your primary database was on. Add your original primary database back into your Data Guard configuration as a physical standby database.

A

Practices and Solutions

Oracle Database 10g: Data Guard Administration A-2

Practice 1: Oracle Data Guard Overview

1. Which one of the following statements is true?a. A standby database is a set of log files that will be applied in the event of a

system failure.b. A primary database is the production database.c. A logical standby is an extension to the physical standby database.d. The redo logs contain native SQL that can be applied to the standby database.

Solution: b

2. Which one of the following is not an Oracle Data Guard service?a. Role managementb. Log transportc. Redo logd. Log apply

Solution: c

3. Which one of the following operations would you perform when the primary database is completely lost?

a. Switchoverb. Apply backups to standbyc. Apply redo logsd. Failover

Solution: d

4. The Oracle Data Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations.

a. Trueb. False

Solution: a

5. Enterprise Manager provides monitoring, automation, and management of the Data Guard broker components.

a. Trueb. False

Solution: a


Practice 1: Oracle Data Guard Overview (continued)

6. Which protection mode will cause the primary database to be shut down if contact with all standby databases is lost?

a. Maximum protectionb. Maximum availabilityc. Maximum performance

Solution: a

7. Which protection mode has the lowest impact on the performance of the primary database but has the possibility of data loss?

a. Maximum protectionb. Maximum availabilityc. Maximum performance

Solution: c

8. Real Application Clusters and Oracle Data Guard should not be used together because they basically do the same thing.

a. Trueb. False

Solution: b


Practice 2-1: Architecture Overview

1. Which one of the following statements is true?a. The ARCn process creates a copy of the online redo logs for use by the LGWR

process.b. The LGWR process collects transaction redo and updates the data files.c. The FAL process provides a client/server mechanism for resolving gaps that

are detected in the range of archive redo logs.d. The MRP process applies archived redo log information to the logical standby

database.Solution: c

2. Which one of the following is not an operational requirement for the Data Guard environment?

a. The primary and standby databases must use the same database release.b. Each primary and standby database must have its own control file.c. The primary database must operate in ARCHIVELOG mode.d. The standby must be on the same node as the primary.

Solution: d

3. What are the modes of a physical standby database?______________________________________________________________________________________________________________Solution: Managed recovery and open read-only

4. What technology is used to transform the redo log into SQL?______________________________________________________________________________________________________________Solution: LogMiner

5. Should you create standby redo logs on the primary database?______________________________________________________Solution: Yes

6. How many standby redo log groups should you have?_____________________________________________________________________________________________________________Solution: At least as many as there are online groups on the primary;one more than this is recommended.


Practice 2-2: Installing the Oracle Management Agent Oracle Enterprise Manager Grid Control is installed and operational on a server for your practices. You must install the Oracle Management Agent on your PC so that you can use Grid Control to monitor, configure, and administer the databases on your PC.

1. Open a terminal window and log on as the oracle user with a password of oracle.

2. Oracle Enterprise Manager Grid Control software is staged in theem10103gc_installmedia directory. Change directories to em10103gc_installmedia/Disk1.

[oracle@EDRSR10P1 oracle]$ cd em10103gc_installmedia/Disk1

3. Set your $ORACLE_HOME environment variable by executing the exportcommand.

[oracle@EDRSR10P1 oracle]$ export ORACLE_HOME=$AGENT_HOME[oracle@EDRSR10P1 oracle]$ echo $ORACLE_HOME/u01/app/oracle/product/10.1.0/agent

4. Invoke the Oracle Universal Installer by issuing the following command:

./runInstaller

5. Click Next on the Welcome page.

6. On the “Specify File Locations” page, accept the defaults in the Source Path and Destination Name fields. Verify that Destination Path is set to/u01/app/oracle/product/10.1.0/agent. Click Next.

7. On the “Set a Product to Install” page, select “Additional Management Agent.” Click Next.

8. On the “Specify Oracle Management Service Location” page, enter the following information about the host machine that Oracle Enterprise Manager Grid Control is installed on:Management Service Host Name: <OMS_host>Management Service Port: 4889

Click Next.

9. Click OK in the Warning dialog box.


Practice 2-2: Installing the Oracle Management Agent

10. Click Install on the Summary page. The Install page appears showing the progress of the installation.

11. The “Setup Privileges” dialog box appears instructing you to execute the root.shscript. Open a new terminal window and log in as the root user.[oracle@EDRSR10P1 oracle]$ su -Password: [root@EDRSR10P1 root]# cd /u01/app/oracle/product/10.1.0/agent[root@EDRSR10P1 root]# ./root.sh

Accept the default values for all prompts during the execution of the root.shscript.After the root.sh script completes, return to the Setup Privileges dialog box andclick OK.

12. The Configuration Assistants page appears. Once the configuration is complete, the “End of Installation” page appears. Verify that the installation was successful and click Exit to exit the Oracle Universal Installer. Click Yes in the Exit dialog box.

13. Configure monitoring credentials for your database. Open your browser and enter the following URL:

http://<oms_host>:7777/em

14. Log in as the user sysman with password oracle1, and change the Monitor Password for your database to oracle.

a. Log in as the user sysman with password of oracle1 and click Login.b. Review the licensing information and click “I agree.”c. Select Targets and click Databases.d. Select your database (<HOSTNAME>_ORCL) from the list of databases and

click Configure.e. Enter the Monitor Password of oracle and click Test Connection.f. Verify the connection is successful and click Next. Click Submit.g. Click OK.


Practice 2-3: Configuring Your Primary Database As you proceed through the remaining practices, you may use this page to record information about your databases.

Primary DatabaseDatabase Name: ___________________________________________________Instance Name: ____________________________________________________Database Unique Name: _____________________________________________Target Name: _____________________________________________________Host: ____________________________________________________________Oracle Home: _____________________________________________________

Standby DatabaseDatabase Name: ___________________________________________________Instance Name: ____________________________________________________Database Unique Name: _____________________________________________Target Name: _____________________________________________________Host: ____________________________________________________________Oracle Home: _____________________________________________________ Type of standby: ___________________________________________________

Standby DatabaseDatabase Name: ___________________________________________________Instance Name: ____________________________________________________Database Unique Name: _____________________________________________Target Name: _____________________________________________________Host: ____________________________________________________________Oracle Home: _____________________________________________________ Type of standby: ___________________________________________________


Practice 2-3: Configuring Your Primary Database (continued)

1. Invoke Enterprise Manager Grid Control and view your database home page.a. Enter the URL supplied by your instructor: http://hostname:7777/emb. Supply the following to log in to Grid Control:

User name: SYSMANPassword: _________

c. Click Login.d. Click Targets to access the Hosts page. e. Click Databases to access the Databases page.f. Select your database by clicking on the database link name.

Important: Because you are logging in as the SYSMAN user, you will be able to see and modify all databases in your class room. Be careful as you select only your database in the list.

2. Configure preferred credentials for your database.a. Access your database home page.b. Click Preferences in the top right corner.c. Click Preferred Credentials on the left side.d. Click the Set Credentials icon for the Database target type.e. Locate your database in the Target Credentials region and enter the usernames

and passwords as follows: Normal username: SYSTEMNormal password: oracleSYSDBA username: SYSSYSDBA password: oracleHost username: oracleHost password: oracle

f. Click Test to verify your entries.g. Click Apply to confirm your entries.

Note: Practice 2-3 continues on the next page.


Practice 2-3: Configuring Your Primary Database (continued)

3. Configure ARCHIVELOG mode for your database. Use the flash recovery area for the archive log destination. Do not set up any other destinations at this time. You must be logged in as SYSDBA to complete this task.

a. On your database home page, click Maintenance to access the Maintenance page.

b. Click Configure Recovery Settings to access the Configure Recovery Settings page.

c. Because you are logged in as SYSTEM, you must click Logout in the upper right corner to change the login user.

d. Select “Log out of Database: hostname_ORCL.oracle.com” and “Display database login page after logout.” Click OK.

e. Enter the username of SYS, password of ORACLE, and select SYSDBA from the “Connect As” drop-down menu. Click Login.

f. On your database home page, click Maintenance to access the Maintenance page.

g. Click Configure Recovery Settings to access the Configure Recovery Settings page.

h. Select “ARCHIVELOG Mode” in the Media Recovery section.i. Accept the default of USE_DB_RECOVERY_FILE_DEST in destination 10 to

indicate that the flash recovery area should be used.j. Click Apply.k. Click Yes on the confirmation page to restart the database instance.l. Confirm the host and database credentials. Click OK.m. Click Yes to restart the database instance after shutdown.n. An Update Message is displayed confirming your change.


Practice 4: Creating a Physical Standby Database with Enterprise Manager

1. Invoke SQL*Plus and enable FORCE LOGGING mode for your database.a. Open a terminal window and invoke SQL*Plus.

[oracle@EDRSR4P1 oracle]$ sqlplus /nologSQL*Plus: Release 10.1.0.3.0 - Production on Wed Dec 1 12:50:51 2004Copyright (c) 1982, 2004, Oracle. All rights reserved.SQL>

b. Connect to your database as SYS with SYSDBA privileges.SQL> connect / as sysdbaConnected.

c. Issue the ALTER DATABASE FORCE LOGGING SQL command.SQL> alter database force logging;Database altered.

2. Invoke Enterprise Manager 10g Grid Control and access your database home page.a. Enter the URL supplied by your instructor: http://hostname:7777/emb. Supply the following to log in to Grid Control:

User name: SYSMANPassword: _________

c. Click Login.d. Click Targets to access the Hosts page. e. Click Databases to access the Databases page.f. Click the link for your database to access the database home page.


Practice 4: Creating a Physical Standby Database with Enterprise Manager (continued)

3. Create a physical standby database with the following specifications by using Grid Control:Primary database unique name: <HOSTNAME>_ORCLStandby database unique and target name: <HOSTNAME>_SITE1Location: Create your physical standby database on the next highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your physical standby database named EDRSR8P1_SITE1 on EDRSR8P2. If you are using EDRSR8P12, create your standby on EDRSR8P1. Note: Your instructor may modify this configuration.

a. Access your database home page and select Administration to access the Administration page.

b. Click Data Guard in the High Availability section.c. Click Add Standby Database to invoke the Add Standby Database Wizard.d. Select “Create a new physical standby database” and click Continue.e. Select “Perform a live backup of the primary database” and click Next.f. Accept the default location for the backup and the default option to delete the

working directory after the standby creation. Click Next.g. Accept the default instance name of dg2. Enter the credentials for the standby

host machine if they differ from the default supplied. Select the host in the Standby Database Oracle Home section as described above. Click Next.

h. Accept the default, to transfer files, in the Backup File Access section. Select “Convert to Oracle OFA” in the Standby Database File Locations section. Accept the default location for the network configuration file location. Click Next.

i. Specify Database Unique Name and Target Name as <HOSTNAME>_SITE1. Accept the default location for the archived redo logs. Click Next.

j. Review your configuration information and click Finish.k. After you are returned to the Data Guard page, select “Real Time: 1 Minute

Refresh” from the View Data drop-down menu to monitor the creation of your standby database. The creation is complete when the status changes to Normal.


Practice 4: Creating a Physical Standby Database with Enterprise Manager (continued)

4. After the physical standby creation is complete, use Verify to validate the configuration and add standby redo logs.

a. Access your Data Guard configuration by selecting your primary database. Select Data Guard in the High Availability section of the Administration page.

b. Click Verify in the Additional Administration section.c. Review the information in the “Detailed Results” section.d. Select “Create standby redo logs for the following database(s)” to create

standby redo logs for your primary and standby databases. Click OK.


Practice 6: Data Protection Modes and Log Transport Services

1. Using Enterprise Manager, change the data protection mode for your standby database to maximum protection.

a. On the Databases target page, click the link for your primary database.b. Click Administration.c. Click Data Guard in the High Availability section.d. In the Overview section, click the link in the Protection Mode field to access

the Edit Protection Mode: Select page. e. Select Maximum Protection and click Continue.f. Accept the default selection of your physical standby database and click OK.g. Click Yes on the Confirmation: Edit Protection Mode page.h. You are returned to the Data Guard Overview page. Verify that your protection

mode has been changed to maximum protection.

2. Using Enterprise Manager, configure a delay for the application of redo to the standby database to allow you to stop the application of any corrupt data. Set the delay for 2 hours (120 minutes).

a. Select your standby database and click Edit on the Data Guard page.b. Click Standby Role Properties on the Edit Standby Database Properties page.c. Enter the delay value of 120 in the Apply Delay field.d. Click Apply.

3. In preparation for later practices, use Enterprise Manager to change the data protection mode back to maximum performance.

a. Navigate to the Data Guard page.b. Click the link in the Protection Mode field to access the Edit Protection Mode:

Select page. c. Select Maximum Performance and click Continue.d. Accept the default selection of your physical standby database and click OK.e. Click Yes on the Confirmation: Edit Protection Mode page.f. You are returned to the Data Guard Overview page. Verify that your protection

mode has been changed to maximum performance.

4. You decide that you no longer want the delayed application of redo. Use Enterprise Manager to disable the delay in the application of redo.

a. Select your standby database and click Edit on the Data Guard page.b. Click Standby Role Properties on the Edit Standby Database Properties page. c. Enter the delay value of 0 in the Apply Delay field.d. Click Apply.


Practice 7: Creating a Logical Standby Database Using Enterprise Manager

1. Create a logical standby database with the following specifications using Enterprise Manager:Standby database unique and target name: <HOSTNAME>_SITE2Location: Create your physical standby database on the next highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your physical standby database named EDRSR8P1_SITE2 on EDRSR8P2. If you are on EDRSR8P12, create your standby on EDRSR8P1. Note: Your instructor may modify this configuration.

a. Select your primary database on the Databases target page.b. Select Administration to access the Administration page.c. Click Data Guard in the High Availability section.d. Click Add Standby Database in the Standby Databases section to invoke the

Add Standby Database Wizard.e. Select “Create a new logical standby database” and click Continue.f. Select “Perform a live backup of the primary database” and click Next.g. Accept the default location for the backup and the default option to delete the

working directory after the standby creation. Enter primary host credentials if needed. Click Next.

h. Accept the default instance name of dg3. Enter the credentials for the host machine if they differ from the default supplied. Select the host in the Standby Database Oracle Home section as described above. Click Next.

i. Accept the default, to transfer files, in the Backup File Access section. Select “Convert to Oracle OFA” in the Standby Database File Locations section. Accept the default location for the network configuration file location. Click Next.

j. Accept the default Database Name. Specify Database Unique Name and Target Name as <HOSTNAME>_SITE2. Accept the default location for the archived redo logs. Click Next.

k. Review your configuration information and click Finish.l. Select "Real Time: 1 Minute Refresh" in the View Data drop-down menu to

monitor the creation.

2. After the logical standby database creation is complete, use Verify to validate the configuration.

a. Access your Data Guard configuration by selecting your primary database. Select Data Guard in the High Availability section of the Administration page.

b. Click Verify in the Additional Administration section.c. View progress on the Processing: Verify page.d. Review results in the Detailed Results window. Click OK to return to the Data

Guard page.


Practice 9: Switchover and Failover

1. Create a table in your primary database defined as follows:Schema: HRName: MY_TABLEColumn Name: COL1 Data type: NUMBERTablespace: EXAMPLE

a. Select your primary database on the Databases target page.b. Select Tables in the Schema section of the Administration page.c. Click Create.d. Select Standard, Heap Organized and then click Continue.e. Enter the table name, schema, tablespace name, and column information. Click

OK.

2. Perform a log switch on your primary database.a. Return to your primary database home page. b. Click Redo Log Groups in the Storage section of the Administration page.c. Select “Switch logfile” in the Actions list.d. Click Go.

3. Access the Data Guard page for your configuration. a. Return to the Administration page for your primary database by clicking on the

database breadcrumb.b. Select Data Guard in the High Availability section of the Administration page.

4. Select your physical standby database and perform a switchover.a. Select your physical standby database and click Switchover.b. Supply host login credentials and click Login.c. Click Yes to confirm the switchover operation.d. View the progress on the Processing: Switchover page.

5. Verify that the HR.MY_TABLE table you created in step 1 exists on your new primary database.

a. Access the database home page for your new primary database.b. Log in to your database as SYS with a password of ORACLE as SYSDBA.c. Select Tables in the Schema section of the Administration page.d. Enter HR in the Schema field and MY_TABLE in the Object Name field.e. Click Go.

Note: Practice 9 continues on the next page.


Practice 9: Switchover and Failover (continued)

6. Perform a complete failover to your physical standby database using Enterprise Manager.

a. Navigate to the Data Guard page.b. Select your physical standby database and click Failover.c. Click Yes to connect to your physical standby database.d. Select Complete for the type of failover and click Yes.e. The Processing: Failover page is displayed. When the failover is completed,

you are returned to the Data Guard page.


Practice 12: Workshop Preparation

To prepare for the workshop, you need to drop your Data Guard configuration and your standby databases. Follow the steps below to accomplish these tasks.

1. Access the Data Guard page and drop your Data Guard configuration by selecting Remove Data Guard Configuration in the Additional Administration section. Click Yes on the Confirmation: Remove Data Guard Configuration page to confirm.

2. Open a terminal window and telnet to the machine your standby databases are on. Log in as the oracle user with password of oracle. Edit the /etc/oratab file on the machine that your standby databases are on to add entries for these databases. The entries use the instance name to reference the instance and database. This step is required so that you will be able to delete the databases using DBCA.Add entries as follows:dg2:/u01/app/oracle/product/10.1.0/db_1:Ndg3:/u01/app/oracle/product/10.1.0/db_1:N

3. Invoke DBCA on the server machine your standby databases are on and delete your standby databases.In a terminal window, logged on as the oracle user, invoke DBCA by entering dbca at the command prompt.

a. Click Next on the DBCA Welcome page.b. Select “Delete a Database” and click Next.c. Select “dg2” and click Finish.d. Click Yes to confirm the deletion.e. Click Yes to perform another operation.f. Repeat the deletion steps for “dg3.”g. After you complete the deletion of dg3, click No to exit DBCA.

4. Remove your <HOSTNAME>_SITE1 and <HOSTNAME>_SITE2 databases from Grid Control.

a. Navigate to the Databases page. b. Select your <HOSTNAME>_SITE1 database and click Remove. c. Click Yes to confirm. d. Repeat for your <HOSTNAME>_SITE2 database.


Practice 12: Workshop Scenarios

1. You need to create a Data Guard configuration to ensure high availability, data protection, and disaster recovery for your enterprise data. You want to be able to open your standby database in read-only mode so that queries can be executed. Create your standby database to meet these requirements with the following specifications:Standby database unique and target name: <YOUR_HOSTNAME>_SITE1Location: Create your standby database on the next highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your physical standby database named EDRSR8P1_SITE1 on EDRSR8P2. If you are on EDRSR8P12, create your standby database on EDRSR8P1.

a. Select your primary database on the Databases page.b. Select Data Guard in the High Availability section of the Administration page.c. On the Data Guard page, click Add Standby Database.d. Select “Create a new physical standby database” and click Continue.e. Select “Perform a live backup of the primary database” and click Next.f. Accept the default location for the Working Directory. Enter the Primary Host

Credentials if not already populated. Click Next.g. Accept the default instance name. Select the host for the Oracle Home and

click Next.h. Select “Transfer files from the primary host working directory to a standby host

working directory” and “Convert to OFA.” Click Next. i. Change the Database Unique Name and Target Name to

<HOSTNAME>_SITE1 as described above. Accept the default for the Standby Archive location. Click Next.

j. Review the information and click Finish.k. When the Data Guard page reappears, select Real Time: 1 Minute Refresh in

the View Data drop-down menu. You can also click the link in the Status column to review additional information.

2. You want to ensure that you have created your standby database successfully and that the log transport and apply services are working. Use Enterprise Manager to confirm that your Data Guard configuration is functioning properly.

a. Click Verify in the Additional Administration section of the Data Guard page.b. Click OK to create standby redo logs.


Practice 12: Workshop Scenarios

3. You understand that Data Guard can automatically detect archive gaps and resolve those gaps by copying the missing sequence of log files to the standby destination. As an example, if connectivity is lost between the primary and one or more standby databases (for example, due to network problems), redo data being generated on the primary database cannot be sent to those standby databases. Once a connection is reestablished, the missing archived redo log files (referred to as a gap) are automatically detected by Data Guard, which then automatically transmits the missing archived redo log files to the standby databases. Verify that this feature is working properly in your configuration by simulating a loss of connectivity. Disable log transport services to your standby database, switch the log on your primary database, and re-enable log transport services to your standby database.

a. Disable log transport services as follows:On the Data Guard page, select the standby database and click Edit. Select the Standby Role Properties page. Expand Show Advanced Properties. Select OFF in the Log Shipping drop-down menu. Click Apply. Select the Databases targets tab.

b. Force three to five log switches on the primary database as follows:Click the link for your primary database on the Databases targets tab.Select Redo Log Groups on the Administration page for the primary database. Select Switch Logfile in the Actions drop-down menu and click Go. Repeat three to five times.Return to the Data Guard page and observe the difference in the current log number for the primary database and the last received log for the standby database.

c. Enable log transport services to the physical standby database as follows:On the Data Guard page, select the standby database and click Edit. Select the Standby Role Properties page. Expand Show Advanced Properties. Select ON in the Log Shipping drop-down menu. Click Apply.

d. Verify that all redo has been applied as follows:Return to the Data Guard page and observe that the standby database has received the redo log files from the primary database.


Practice 12: Workshop Scenarios (continued)

4. Maximum performance is the default protection mode and provides the highest level of data protection that is possible without affecting the performance of the primary database. This is accomplished by allowing a transaction to commit as soon as the redo data needed to recover that transaction is written to the local online redo log. You have determined that you need to change the data protection mode to ensure the redo data needed to recover each transaction is written to both the local online redo log and to the standby redo log on at least one standby database before the transaction commits. You also want to configure the protection mode so that the primary database does not shut down if a fault prevents it from writing its redo stream to a remote standby redo log. Change the protection mode so that your configuration meets these requirements. Change the protection mode to maximum availability as follows:

a. On the Data Guard page, click the link in the Protection Mode field.b. Select Maximum Availability and click Continue.c. Click OK on the Edit Protection Mode: Standby Databases and Redo Logs

page.d. Click Yes on the Confirmation: Edit Protection Mode page.

5. You want to ensure fast switchover and failover times should you need to perform those operations. Configure the Data Guard feature that enables log apply services to apply redo data as it is received, without waiting for the current standby redo log file to be archived.Enable real-time apply for your Data Guard configuration as follows:

a. On the Data Guard page, select your standby database and click Edit.b. Click Standby Role Properties.c. Expand Show Advanced Properties.d. Select ON from the Real Time Apply drop-down menu.e. Click Apply.f. Return to the Data Guard page by clicking the Data Guard breadcrumb.



6. You want to ensure that you will not need to re-create the primary database after you have performed a failover operation. Configure the feature that will enable you to flash back the failed primary database to a point in time before the failover and convert it into a standby database for the new primary database.Enable Flashback Database for your primary database, setting the retention time to 12 hours as follows:

a. Navigate to the Maintenance page for your primary database.b. Select Configure Recovery Settings in the Backup/Recovery section of the

Maintenance page.c. Select “Enable flashback logging for fast database point-in-time recovery.”d. Enter 12 hours in the “Flashback Retention Time” field.e. Click Apply.f. Click Yes to restart the database instance.g. Enter the Host Credentials and Database Credentials if they are not supplied.

Click OK.h. Click Yes to restart the database instance.i. Return to the database home page after the database instance has been restarted.

7. You have been asked to add an additional data file to the EXAMPLE tablespace in your primary database. Add the data file with the following specifications:Data file name: /u01/app/oracle/oradata/orcl/example02.dbfData file size: 2 MBVerify that the new data file has been added to your standby database.

a. Add the new tablespace as follows:Select the primary database. Select Tablespaces in the Storage section of the Administration page. Select the EXAMPLE tablespace. Select Add Datafile in the Actions drop-down menu and click Go. Enter example02.dbf in the File Name field and 2 MB in the File Size field. Click OK.An update message is displayed.



b. Force a log switch as follows:Return to the database home page.Select Redo Log Groups on the Administration page for the primary database. Select Switch Logfile in the Actions drop-down menu and click Go.

c. Verify that the new data file was added to the standby database as follows:Open a terminal window and telnet to the machine your standby database is on. Log in as the oracle user with password of oracle. You must start a SQL*Plus session to verify that the new data file was added to the standby database. Because the database is in MOUNT mode, EM does not display the tablespaces and datafiles. Issue the following query to verify that the file was added:SELECT name FROM v$datafile;

Sample output is as follows:[oracle@EDRSR4P1 oracle]$ export ORACLE_SID=dg2

[oracle@EDRSR4P1 oracle]$ sqlplus /nolog

SQL*Plus: Release 10.1.0.3.0 - Production on Thu Dec 9 13:08:28 2004

Copyright (c) 1982, 2004, Oracle. All rights reserved.

SQL> connect / as sysdba

Connected.

SQL> SELECT db_unique_name FROM v$database;

DB_UNIQUE_NAME

------------------------------

EDRSR10P1_SITE1

SQL> SELECT name FROM v$datafile;

NAME

----------------------------------------------------------------

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/system01.dbf

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/undotbs01.dbf

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/sysaux01.dbf

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/users01.dbf

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/example01.dbf

/u01/app/oracle/product/10.1.0/db_1/oradata/dg2/example02.dbf

6 rows selected.



8. The application users need to run some additional reports and do not want to impact the production system. Perform the steps required to make the standby database available for this reporting task. Verify that you can query tables in the standby database and then restart real-time apply so that the standby database will be resynchronized with the primary database.

a. On the Data Guard page, select the standby database and click Edit. b. Select “Read Only” in the Log Apply Services section. Click Apply.c. Return to the Data Guard page and verify the status of Normal, Read-only for

your standby database.d. Open a terminal window and telnet to the machine your standby database is on.

Log in as the oracle user with password of oracle. Invoke SQL*Plus. Connect as the HR user and query the HR.EMPLOYEES table as follows:SQL> SELECT count(*) FROM employees;





SQL> connect hr/hr

Connected.

SQL> SELECT count(*) FROM employees;

COUNT(*)

----------

107

SQL> exit

Disconnected from Oracle Database 10g Enterprise Edition Release10.1.0.3.0 -

With the Partitioning, OLAP and Data Mining options

e. On the Data Guard page, select the standby database and click Edit. f. Select Online in the Log Apply Services section. Click Apply.g. Return to the Data Guard page and verify the status of Normal for your standby

database.



h. Open a terminal window and telnet to the machine your standby database is on. Log in as the oracle user with password of oracle. Invoke SQL*Plus. Connect as the HR user and attempt to query the HR.EMPLOYEES table as follows:SQL> SELECT count(*) FROM employees;

Sample output is as follows:[oracle@EDRSR4P1 oracle]$ sqlplus /nolog



SQL> connect hr/hr

ERROR:

ORA-00604: error occurred at recursive SQL level 1

ORA-01219: database not open: queries allowed on fixed tables/views only

9. You have determined that the users will need to run reports on a regular basis and do not want to impact the production database. In addition, you would like to add an additional standby database to your configuration for additional data protection. Configure a second standby database that will be available for users to perform queries, summations, and reporting activities against at all times with the following specifications:Standby database unique and target name: <HOSTNAME>_SITE2Location: Create your standby database on the next highest student PC in your classroom. For example, if your host name is EDRSR8P1, create your standby database on EDRSR8P2. If you are on EDRSR8P12, create your standby database on EDRSR8P1.

a. On the Data Guard page, click Add Standby Database.b. Select “Create a new logical standby database” and click Continue.c. Select “Perform a live backup of the primary database” and click Next.d. Accept the default location for the Working Directory. Enter the Primary Host

Credentials if not already populated. Click Next.e. Accept the default instance name. Select the host for the Oracle Home and

click Next.f. Select “Transfer files from the primary host working directory to a standby host

working directory” and “Convert to OFA.” Click Next. g. Change the Database Unique Name and Target Name to

<HOSTNAME>_SITE2 as described above. Click Next.



h. Review the information and click Finish.i. When the Data Guard page reappears, select “Real Time: 1 Minute Refresh”

from the View Data drop-down menu. You can also click the link in the Status column to review additional information.

10. Verify that the automatic gap detection and resolution feature is working properly in your configuration by simulating a loss of connectivity to your new standby database. Disable log transport services to your standby database, switch the log on your primary database, and re-enable log transport services to your standby database.

a. Disable log transport services to the logical standby database as follows:On the Data Guard page, select the logical standby database and click Edit. Select the Standby Role Properties page. Expand Show Advanced Properties. Select OFF in the Log Shipping drop-down menu. Click Apply.Return to the Databases target page.

b. Force three to five log switches on your primary database as follows:Select your primary database on the Database target page by clicking on the linkSelect Redo Log Groups on the Administration page for the primary database. Select Switch Logfile in the Actions drop-down menu and click Go. Repeat three to five times.Return to the Data Guard page and observe the difference in the current log number for the primary database and the last received log for the logical standby database.

c. Enable log transport services to the logical standby database as follows:On the Data Guard page, select your logical standby database and click Edit. Select the Standby Role Properties page. Expand Show Advanced Properties. Select ON in the Log Shipping drop-down menu. Click Apply.

d. Verify that all redo has been applied to the logical standby database as follows:Return to the Data Guard page and observe that the standby database has received the redo log files from the primary database.



11. Because the users want to use some tables in the new standby database to report against for historical purposes, you need to configure SQL Apply so that certain DML statements are not executed against those tables on the logical standby database. You decide to test this feature first by creating a new table on the primary database as follows:CREATE TABLE hr.emp_name

AS SELECT first_name, last_name

FROM hr.employees

WHERE 1=2;

Define a filter that prevents SQL Apply from issuing DML statements against the HR.EMP_NAME table on the logical standby database. Insert a few rows into the HR.EMP_NAME table on the primary database and commit your changes. Force a log switch on the primary database and then verify that the new rows are not applied to your logical standby database.

a. Open a terminal window.b. Change to the labs directory.c. Invoke SQL*Plus and connect as hr/hr. Execute the lab_12_11_a.sql

script in your labs directory to create the HR.EMP_NAME table as described. Maintain the SQL*Plus session for later steps.

d. Configure SQL Apply on the logical standby database so that no DML statements are executed against the HR.EMP_NAME as follows:Navigate to the Data Guard page.Select the logical standby database and click Edit.Click Standby Role Properties.Expand Show Advanced Properties.Click Add in the Skip Table Entries section.Enter the following information in the specified fields:SQL Statement: DMLSchema: HRObject Name: EMP_NAMESelect “Always skip this statement type.”Click OK. Verify the information in the Skip Table Entries section and click Apply.A success message is displayed.



e. In your SQL*Plus session, execute the lab_12_11_c.sql script in the labs directory to insert two rows in the HR.EMP_NAME table as follows:INSERT INTO hr.emp_name

VALUES ('Don','Miller');

INSERT INTO hr.emp_name

VALUES ('Sally','Hebert');

COMMIT;

f. On your primary database, force a log switch as follows:Access the Maintenance page for your primary database.Click Redo Log Groups.Select Switch logfile in the Actions drop-down menu and click Go.

g. Access your logical standby database and query the HR.EMP_NAME table to determine if any rows have been inserted into the table as follows:Open a terminal window and telnet to the machine your standby database is on. Log in as the oracle user with password of oracle. Invoke SQL*Plus for your logical standby database.Connect as hr/hr.Issue the following command:SELECT count(*) FROM emp_name;

There should be no rows in the emp_name table.Sample output is as follows:[oracle@EDRSR4P1 oracle]$ export ORACLE_SID=dg3


SQL*Plus: Release 10.1.0.3.0 - Production on Fri Dec 10 09:08:55 2004


SQL> connect hr/hr

Connected.

SQL> SELECT count(*) FROM emp_name;

COUNT(*)

----------

0



12. You have been asked to create a view for the users to query on the logical standby database. Create the view as follows:CREATE VIEW hr.emp_90_vw

AS SELECT *

FROM hr.employees

WHERE department_id=90;

a. Invoke SQL*Plus and connect to your logical standby database as the SYSuser. Set the Data Guard guard to STANDBY so that you can create a view by issuing the following statement:ALTER DATABASE GUARD STANDBY;






Connected.

SQL> ALTER DATABASE GUARD STANDBY;

Database altered.

b. Connect to your logical standby database as HR, with HR as the password. Create a view on the HR.EMPLOYEES table as follows:CREATE VIEW emp_90_vw

AS SELECT *

FROM employees

WHERE department_id=90;

You can use the lab_12_12_b.sql script to create the view.c. Connect to your logical standby database as SYS and set the Data Guard guard

back to ALL as follows:ALTER DATABASE GUARD ALL;

Sample output is as follows:SQL> connect / as sysdba

Connected.

SQL> ALTER DATABASE GUARD ALL;

Database altered.



13. You have experienced a failure on your primary database server. Fail over to your physical standby database.

a. On the Data Guard page, select your physical standby database and click Failover.On the Confirmation: Redirect page, click Yes to continue with the failover.On the Confirmation: Failover page, select Complete and click Yes.The Processing: Failover page is displayed.The Data Guard page is displayed after processing completes.

b. Force one or two log switches as follows:Click on the link for your new primary database.Select the Administration page and click Redo Log Groups.Select “Switch logfile” in the Actions drop-down menu and click Go. Repeat.Return to the Data Guard page.

14. Your logical standby database is disabled after the failover. Enable your logical standby database.

a. Access the Data Guard page. Your logical standby database shows a status of “Disabled.” Click the “Disabled” link.

b. On the Edit Standby Database Properties page, click Enable. The logical standby database is reset and is now part of your configuration.

c. Click Verify to verify your Data Guard configuration.d. Review the results of the verify and click OK to return to the Data Guard

configuration.



15. You have been able to restore the server on which your primary database was originally located. Add your original primary database back into your Data Guard configuration as a physical standby database.

a. Open a terminal window and telnet to the machine your standby database is on. Log in as the oracle user with password of oracle. On the NEW primary database, issue the follow query in SQL*Plus:SELECT standby_became_primary_scn FROM v$database;

Make note of the SCN value you obtained in the query:_____________________Sample output is as follows:[oracle@EDRSR4P1 oracle]$ export ORACLE_SID=dg2





Connected.

SQL> SELECT db_unique_name, database_role

2 FROM v$database;

DB_UNIQUE_NAME DATABASE_ROLE

------------------------------ ----------------

EDRSR10P1_SITE1 PRIMARY

SQL> SELECT standby_became_primary_scn

2 FROM v$database;

STANDBY_BECAME_PRIMARY_SCN

--------------------------

1710595



b. Using SQL*Plus, start the old primary database instance and place the database in MOUNT mode.STARTUP MOUNT;

Sample output is as follows:[oracle@EDRSR10P1 oracle]$ sqlplus /nolog




Connected to an idle instance.

SQL> STARTUP MOUNT;

ORACLE instance started.

Total System Global Area 188743680 bytes

Fixed Size 778312 bytes

Variable Size 70262712 bytes

Database Buffers 117440512 bytes

Redo Buffers 262144 bytes

Database mounted.

c. Flashback the old primary database to the SCN value you determined in step a.FLASHBACK DATABASE TO BEFORE SCN <SCN>;

Your old primary database is now serving as a new physical standby database.Sample output is as follows:SQL> FLASHBACK DATABASE TO BEFORE SCN 1710595;

Flashback complete.

d. On the new physical standby database, disable Flashback Database.ALTER DATABASE FLASHBACK OFF;

Sample output is as follows:SQL> ALTER DATABASE FLASHBACK OFF;

Database altered.



e. On the new physical standby database, determine the names of the control files by issuing the following command:SELECT name FROM v$controlfile;

Sample output is as follows:SQL> SELECT name FROM v$controlfile;

NAME

-----------------------------------------------------------

/u01/app/oracle/oradata/orcl/control01.ctl



f. On the new physical standby database, create the standby control file:ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'control_file_name';

Sample output is as follows:SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE

2 AS '$ORACLE_BASE/oradata/orcl/sb_control.ctl';

SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE

2 AS '$ORACLE_BASE/oradata/orcl/sb_control.ctl';

Database altered.

g. Shut down the new physical standby database:SHUTDOWN IMMEDIATE;

Sample output is as follows:SQL> SHUTDOWN IMMEDIATE;

ORA-01109: database not open

Database dismounted.

ORACLE instance shut down.



h. Using operating system commands, copy the newly created control (step f) to the locations of your existing control files (as determined in step e).Sample output is as follows:[oracle@EDRSR10P1 oracle]$ cd $ORACLE_BASE/oradata/orcl

[oracle@EDRSR10P1 orcl]$ ls

control01.ctl example02.dbf orcl_srl3.f sb_control.ctl undotbs01.dbf

control02.ctl orcl_srl0.f redo01.log sysaux01.dbf users01.dbf

control03.ctl orcl_srl1.f redo02.log system01.dbf

example01.dbf orcl_srl2.f redo03.log temp01.dbf

[oracle@EDRSR10P1 orcl]$ cp sb_control.ctl control01.ctl

cp: overwrite `control01.ctl'? y





i. Start the instance and mount the database using your new control files:STARTUP MOUNT;

Sample output is as follows:[oracle@EDRSR10P1 orcl]$ sqlplus /nolog




Connected to an idle instance.

SQL> startup mount

ORACLE instance started.

Total System Global Area 188743680 bytes

Fixed Size 778312 bytes

Variable Size 70262712 bytes

Database Buffers 117440512 bytes

Redo Buffers 262144 bytes

Database mounted.



j. Enable flashback database:ALTER DATABASE FLASHBACK ON;

Sample output is as follows:SQL> ALTER DATABASE FLASHBACK ON;

Database altered.

k. Ensure your listener is started, by issuing the following command at the operating system prompt:lsnrctl status listener;

l. You can use Enterprise Manager to enable the physical standby database as follows:Access the Data Guard page. Your new physical standby database shows a status of “Disabled.” Click the “Disabled” link.On the Edit Standby Database Properties page, click Enable. The new physical standby database is reset and is now part of your configuration.Click Verify to verify your Data Guard configuration.Review the results of the verify and click OK to return to the Data Guard configuration.

B

Oracle Data Guard: History

Oracle Database 10g: Data Guard Administration B-2


History of Oracle Data Guard

• Oracle 7.3: Custom standby database• Oracle8i: Automated standby

– Read-only database– Managed recovery– Remote archiving

• Oracle8i Data Guard:– Automation– Single-command switchover and failover– Oracle Parallel Server (OPS) and Oracle Parallel Fail

Safe (OPFS) support

History of Oracle Data GuardOracle 7.3 was the first release to support standby databases. At that time, the process of transmitting redo logs was completely manual.The first version of Oracle8i introduced the ability to automatically ship redo log files from the primary database to the standby database and to have them be automatically applied. It was also possible to stop the recovery process and open the standby database in read-only mode.Oracle8i Data Guard provided a set of scripts for AIX, Solaris, and HP/UX that simplified the installation, monitoring, and management of an Enterprise Edition standby database. It also provided a command-line interface with commands such as SWITCHOVER and FAILOVER to automate the manual steps to perform those actions. The 3.0 versions of the product supported Oracle Parallel Server (OPS) and Oracle Parallel Fail Safe (OPFS) 3.0. Oracle8i Data Guard supported all Oracle8i releases.



History of Oracle Data Guard

• Oracle Data Guard in Oracle9i, Release 1:– Integrated zero-data-loss capability– Data Guard broker, with Data Guard Manager GUI

interface and command-line interface (CLI)– Switchover and failover operations– Automatic gap resolution and resynchronization

• Oracle Data Guard in Oracle9i, Release 2:– Logical standby databases– Maximum protection, maximum availability, and

maximum performance data protection modes– Enhanced Data Guard broker functionality– Cascaded redo log destinations

History of Oracle Data Guard (continued)Oracle9i, Release 1, introduced the new concept of protection mode, preventing the primary and the standby databases from diverging. The Data Guard broker (with a GUI interface called Data Guard Manager integrated with Enterprise Manager) was also introduced. In addition, a command-line interface (CLI) called DGMGRL was made available.With Oracle9i, Release 2, Data Guard continued to be enhanced with the addition of logical standby databases. Three protection modes were introduced to replace the modes of protection that were available in previous releases. The Data Guard broker was enhanced to support up to nine physical or logical standby databases. In addition, the broker supported switchover and failover operations with this release.



Oracle Data Guard Release 10.1

• Real-time apply• Recovery through OPEN RESETLOGS• Flashback Database support• Simplified configuration management with the

VALID_FOR attribute• Standby redo log support on logical standby

databases• Improved redo data transmission security• Improved Data Guard support for RAC• Zero downtime instantiation of logical

standby databases

Oracle Data Guard Release 10.1Data Guard in Oracle Database 10g has been enhanced to provide:

• Additional ease-of-use features• Integration with new Oracle Database high availability features such as Flashback

Database• Comprehensive features and functionality

This course focuses on the Oracle Data Guard product and all of its features that are available in Release 10.1.

Documents

Oracle10g - Data Guard Administration - D40345