Chap 12 Corrected

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Chapter 12

Data and

DatabaseAdministration

Modern Database ManagementModern Database Management

88thth EditionEdition

Jeffrey A. Hoffer, Mary B. Prescott,Jeffrey A. Hoffer, Mary B. Prescott,

Fred R. McFaddenFred R. McFadden2

007byPrenticeHall

FAROOQ

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Chapter 12

Objectives

Definition of terms

List functions and roles of data/databaseadministration

Describe role of data dictionaries and information

repositories Compare optimistic and pessimistic concurrency

control

Describe problems and techniques for data

security Describe problems and techniques for data

recovery

Describe database tuning issues and list areaswhere changes can be done to tune the database

Describe importance and measures of data

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Chapter 12

Traditional AdministrationDefinitions Data AdministrationData Administration: A high-level

function that is responsible for theoverall management of data resourcesin an organization, includingmaintaining corporate-wide definitionsand standards

Database AdministrationDatabase Administration: Atechnical function that is responsiblefor physical database design and fordealing with technical issues such assecurity enforcement, databaseperformance, and backup and recovery

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Traditional DataAdministration Functions Data policies, procedures, standards

Planning

Data conflict (ownership) resolution

Managing the information repository

Internal marketing of DA concepts

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Traditional DatabaseAdministration Functions Selection of DBMS and software tools

Installing/upgrading DBMS

Tuning database performance

Improving query processing performance

Managing data security, privacy, and integrity

Data backup and recovery

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Evolving Approaches toData Administration Blend data and database administration into

one role

Fast-track development monitoringdevelopment process (analysis, design,

implementation, maintenance) Procedural DBAsmanaging quality of triggers

and stored procedures

eDBAmanaging Internet-enabled database

applications PDA DBAdata synchronization and personal

database management

Data warehouse administration 6

D W h


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Data WarehouseAdministration New role, coming with the growth in data

warehouses Similar to DA/DBA roles

Emphasis on integration and coordination ofmetadata/data across many data sources

Specific roles: Support DSS applications

Manage data warehouse growth

Establish service level agreements regarding datawarehouses and data marts

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Chapter 12

Open Source DBMSs

An alternative to proprietary packages such asOracle, Microsoft SQL Server, or Microsoft Access

mySQL is an example of open-source DBMS

Less expensive than proprietary packages

Source code available, for modification

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Figure 12-2 Data modeling responsibilities


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Chapter 12

Database Security

Database Security:Database Security:Protection of the data against

accidental or intentional loss,destruction, or misuse

Increased difficulty due to

Internet access andclient/server technologies

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Figure 12-3 Possible locations of data security threats


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Threats to Data Security

Accidental losses attributable to: Human error

Software failure

Hardware failure

Theft and fraud

Improper data access: Loss of privacy (personal data)

Loss of confidentiality (corporate data) Loss of data integrity

Loss of availability (through, e.g.sabotage)

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Figure 12-4 Establishing Internet Security


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Chapter 12

Web Security

Static HTML files are easy to secure Standard database access controls Place Web files in protected directories on

server

Dynamic pages are harder Control of CGI scripts User authentication Session security

SSL for encryption Restrict number of users and open ports Remove unnecessary programs

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W3C Web PrivacyStandard Platform for Privacy Protection (P3P)

Addresses the following:

Who collects data

What data is collected and for what purpose Who is data shared with

Can users control access to their data

How are disputes resolved

Policies for retaining data

Where are policies kept and how can they beaccessed 15


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Chapter 12

Database SoftwareSecurity Features

Views or subschemas

Integrity controls

Authorization rules

User-defined procedures Encryption

Authentication schemes

Backup, journalizing, and checkpointing

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Views and IntegrityControls Views

Subset of the database that is presented toone or more users

User can be given access privilege to viewwithout allowing access privilege tounderlying tables

Integrity Controls

Protect data from unauthorized use Domainsset allowable values

Assertionsenforce database conditions 17


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Authorization Rules

Controls incorporated in the datamanagement system

Restrict: access to data

actions that people can take on data

Authorization matrix for: Subjects

Objects

Actions

Constraints18


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Figure 12-5 Authorization matrix


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Some DBMSs also provide

capabilities for

to customize theauthorization process

Figure 12-6a Authorization table for subjects (salespeople)

Figure 12-6b Authorization table for objects (orders)

Figure 12-7 Oracle privileges

Implementing

authorizationrules


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the codingor scrambling of data sothat humans cannot read

them

Secure Sockets Layer(SSL) is a popularencryption scheme for

TCP/IP connections

Figure 12-8 Basic two-key encryption


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Authentication Schemes Goal obtain a positive identification of the user

Passwords: First line of defense Should be at least 8 characters long

Should combine alphabetic and numeric data

Should not be complete words or personalinformation

Should be changed frequently

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u en ca on c emes


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u en ca on c emes(cont.)

Strong Authentication

Passwords are flawed: Users share them with each other

They get written down, could be copied

Automatic logon scripts remove need to explicitlytype them in

Unencrypted passwords travel the Internet

Possible solutions:Two factore.g. smart card plus PIN

Three factore.g. smart card, biometric, PIN

Biometric devicesuse of fingerprints, retinalscans, etc. for positive ID

Third-party mediated authenticationusingsecret keys, digital certificates 23


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Procedures Personnel controls

Hiring practices, employee monitoring, security training

Physical access controls Equipment locking, check-out procedures, screen

placement

Maintenance controls Maintenance agreements, access to source code, quality

and availability standards

Data privacy controls Adherence to privacy legislation, access rules

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Database Recovery

Mechanism for restoring a database quickly andaccurately after loss or damage

Recovery facilities:

Backup Facilities

Journalizing Facilities Checkpoint Facility

Recovery Manager

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Back-up Facilities

Automatic dump facility that produces backup copyof the entire database

Periodic backup (e.g. nightly, weekly)

Cold backupdatabase is shut down during backup

Hot backupselected portion is shut down andbacked up at a given time

Backups stored in secure, off-site location

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Journalizing Facilities Audit trail of transactions and database updates

Transaction logrecord of essential data for eachtransaction processed against the database

Database change logimages of updated data Before-imagecopy before modification

After-imagecopy after modification

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Figure 12-9 Database audit trail

From the backup and

logs, databases can berestored in case ofdamage or loss


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Checkpoint Facilities

DBMS periodically refuses to accept new transactions

system is in a quietstate

Database and transaction logs are synchronized

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Recovery and RestartProcedures

Disk Mirroringswitch between identicalcopies of databases

Restore/Rerunreprocess transactions

against the backupTransaction Integritycommit or abort

all transaction changes Backward Recovery (Rollback)apply

before images Forward Recovery (Roll Forward)apply

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Transaction ACIDProperties Atomic

Transaction cannot be subdivided

Consistent Constraints dont change from before

transaction to after transaction Isolated

Database changes not revealed to usersuntil after transaction has completed

Durable Database changes are permanent

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Figure 12-10 Basic recovery techniquesa) Rollback

Figure 12 10 Basic recovery techniques (cont )


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Figure 12-10 Basic recovery techniques (cont.)b) Rollforward

Database Failure


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Database FailureResponses

Aborted transactions Preferred recovery: rollback Alternative: Rollforward to state just prior to abort

Incorrect data Preferred recovery: rollback

Alternative 1: rerun transactions not including inaccurate

data updates Alternative 2: compensating transactions

System failure (database intact) Preferred recovery: switch to duplicate database

Alternative 1: rollback

Alternative 2: restart from checkpoint Database destruction

Preferred recovery: switch to duplicate database

Alternative 1: rollforward

Alternative 2: reprocess transactions

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Chapter 12

Concurrency Control

Problemin a multiuser environment, simultaneousaccess to data can result in interference and dataloss

SolutionConcurrency ControlConcurrency Control

The process of managing simultaneous operationsagainst a database so that data integrity ismaintained and the operations do not interfere witheach other in a multi-user environment

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Figure 12 11 Lost update (no concurrency control in effect)


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Figure 12-11 Lost update (no concurrency control in effect)

Simultaneous access causes updates to cancel each other

A similar problem is the problem


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Concurrency ControlTechniques

Serializability Finish one transaction before starting another

Locking Mechanisms The most common way of achieving serialization

Data that is retrieved for the purpose of updating islocked for the updater

No other user can perform update until unlocked

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Fi 12 12 U d t ith l ki ( t l)


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Figure 12-12: Updates with locking (concurrency control)


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Locking Mechanisms Locking level:

Databaseused during database updates

Tableused for bulk updates

Block or pagevery commonly used

Recordonly requested row; fairly commonly

used Fieldrequires significant overhead;

impractical

Types of locks: Shared lockRead but no update permitted.

Used when just reading to prevent anotheruser from placing an exclusive lock on therecord

Exclusive lockNo access permitted. Usedwhen preparing to update

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Deadlock An impasse that results when two or more

transactions have locked common resources,and each waits for the other to unlock theirresources

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Figure 12-13The problem of deadlock

John and Marsha will waitJohn and Marsha will wait

forever for each other toforever for each other to

release their lockedrelease their locked

resources!resources!


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Managing Deadlock

Deadlock prevention: Lock all records required at the beginning of

a transaction

Two-phase locking protocol Growing phase

Shrinking phase

May be difficult to determine all neededresources in advance

Deadlock Resolution:

Allow deadlocks to occur Mechanisms for detecting and breaking

them Resource usage matrix

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Versioning

Optimistic approach to concurrencycontrol

Instead of locking

Assumption is that simultaneousupdates will be infrequent

Each transaction can attempt an updateas it wishes

The system will reject an update when itsenses a conflict

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Figure 12-15 The use of versioning

Better performance than locking


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Managing Data Quality

Causes of poor data quality External data sources Redundant data storage Lack of organizational commitment

Data quality improvement Perform data quality audit Establish data stewardship program (data

stewardis a liaison between IT and businessunits)

Apply total quality management (TQM)practices

Overcome organizational barriers Apply modern DBMS technology

Estimate return on investment

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Data Dictionaries and


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Data Dictionaries andRepositories

Data dictionary

Documents data elements of a database

System catalog

System-created database that describes alldatabase objects

Information Repository Stores metadata describing data and data

processing resources Information Repository Dictionary System (IRDS)

Software tool managing/controlling access to

information repository

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Figure 12-16 Three components of the repository system


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g p p y yarchitecture

A schema of the

repositoryinformation

Softwarethat

managestherepositoryobjects

Where repositoryobjects are stored

: adapted from Bernstein, 1996.

Database Performance


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Database PerformanceTuning

DBMS Installation

Setting installation parameters Memory Usage

Set cache levels

Choose background processes

Input/Output (I/O) Contention Use striping

Distribution of heavily accessed files

CPU Usage Monitor CPU load

Application tuning Modification of SQL code in applications 47


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Data Availability

Downtime is expensive How to ensure availability

Hardware failuresprovide redundancy for fault tolerance

Loss of datadatabase mirroring

Maintenance downtimeautomated and nondisruptivemaintenance utilities

Network problemscareful traffic monitoring, firewalls,and routers

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