Oracle 12.2 - My Favorite Top 5 New or Improved Features

Oracle 12.2 – My Favorite Top Five New or Improved FeaturesJanis Griffin

Senior DBA / Performance Evangelist

© 2018 SolarWinds Worldwide, LLC. All rights reserved.

Who Am I

• Senior DBA / Performance Evangelist for SolarWinds• Janis.Griffin@solarwindscom• Twitter® - @DoBoutAnything• Current – 25+ Years in Oracle®, SQL Server®, ASE, MySQL®• DBA and Developer

• Specialize in Performance Tuning• Review Database Performance for Customers and Prospects• Common Question – How do I tune it?

mailto:[email protected]


Agenda

• In-Memory Option• How it works• Virtual Columns, join groups

• SQL, Dictionary, and Optimizer Enhancements• New Functions and Syntax

• Approximate and First n Rows• SQLPlus Improvements

• PDB Improvements• Hot Clone• Memory Management

• New Partitioning Features• Sharding Capabilities

• The ‘Horizontal’ Database


Memory – In The Beginning…

• 9i - SGA_MAX_SIZE • Memory could grow/shrink

• DB_CACHE_SIZE• No more DB_BLOCK_BUFFERS

• 10g - Automatic Shared Memory Management (ASMM)• SGA_TARGET

• Set minimum values for • Data Cache, Large Pool• Shared Pool, Java Pool

• 11g - MEMORY_TARGET (AMM)• Sets SGA + PGA size together• Can still control minimum sizes - e.g., PGA_AGGREGATE_LIMIT (new in 12c)

• 12c - INMEMORY_SIZE• Set the size of IN-MEMORY Column Store

12c In-Memory Option

• Designed for mixed workloads • Can combine OLAP with OLTP queries • No more Data Warehouse (maybe)

• Dual-format architecture doesn’t double memory requirements• Approximately less than a 20% additional memory overhead

• No additional storage costs or synchronization issues• No changes to application code

• Optimizer is fully aware of the column format• Routes analytic queries to the column format• OLTP operations to the row format

• Only objects with the INMEMORY attribute • Can be in the IN-Memory Column Store (IM)• Works on tablespaces, tables, partitions, sub-partitions or materialized views


12c In-Memory Option


http://www.oracle.com/technetwork/database/in-memory/overview/twp-oracle-database-in-memory-2245633.pdf

Transactions in

Buffer CacheAnalytics in In-Memory

Column Store

http://www.oracle.com/technetwork/database/in-memory/overview/twp-oracle-database-in-memory-2245633.pdf

IM – Why Use it?

• Access only the column data needed• Can prioritize when IM is populated

• Partially load some columns at startup• Load other columns when accessed

ALTER TABLE customers INMEMORY PRIORITY CRITICAL;

• In compressed format • Saves space• Can scan or filter compressed data

• Only decompressed when used in the result set

CREATE TABLE test (c1 NUMBER, c2 NUMBER, c3 CLOB)INMEMORY MEMCOMPRESS FOR QUERY NO INMEMORY(c3),INMEMORY MEMCOMPRESS FOR CAPACITY HIGH (c2);

• DBMS_COMPRESSION (advisor)• Now supports IM compression


IM – Why So Fast

• IM is made up of multiple In-Memory Compression Units (IMCUs)• Background worker processes allocate their own IMCUs

• Then populates their subset of database blocks• Works with the IMCO (In-Memory Coordinator) background process

• Uses SIMD Vector processing• Definition: Single Instruction processing Multiple Data values• Allows a set of column values to be evaluated simultaneously in one CPU instruction• Look at V$STATNAME

• ‘IM scan CUs columns accessed’, 'IM scan segments minmax eligible', 'IM scan CUs pruned');

• New in 12.2 – IM FastStart• Allows for checkpoint of IMCUs to FastStart area on disk• Takes up storage space but less CPU intensive on startup


BEGIN

dbms_inmemory_admin.faststart_enable('FS_TBS');

END;

Best for queries that scan

large amounts of data or

compute values on the fly

IM – Why So Fast

• IM Storage Indexes• Automatically created and maintained on each column in the column store• Allow pruning to occur based on filter predicates in the query• Keeps track of min/max values for each column in an IMCU

• Helps to avoid scans of IM column store

• New in 12.2 - In-Memory Expressions• Materialize commonly used expressions

• Prevents re-computation for every row• Are derived values that take advantage of IM

• Can be done in one of 2 ways• Expression Statistics Store(ESS) automatically stores top 20 popular expressions

• Manage with DBMS_INMEMORY_ADMIN package• Set with INMEMORY_EXPRESSIONS_USAGE parameter

• In-Memory Virtual Columns• Needs INMEMORY_VIRTUAL_COLUMNS parameter set to ENABLED or MANUAL


IM - How To Use It

• IM column store is disabled by default (requires re-start)• Set INMEMORY_SIZE parameter to enable• Needs to be set to 100mb or higher

• New in 12.2 - Can increase on the fly at 128mb or higher

• Part of SGA • May need to increase SGA_TARGET / MEMORY_TARGET


IM - Enable It


IM – How To Use It

• Objects must have the INMEMORY attribute to use the IM column store• Can be tablespace, table, (sub)partition or materialized view• To view objects in column store – see V$IM_SEGMENTS, V$IM_COLUMN_LEVEL, any V$IM% views


IM Performance

• No IM IM•


IM Virtual Columns Example – New 12.2 Feature


alter system set inmemory_virtual_columns = ENABLE;

IM Joins

• In-Memory Joins• Bloom Filters (10g)

• Transforms join into a filter if there are filtering predicates• Can be used in column format via SIMD vector processing

• New in 12.2 – Join Groups• Can be used when there are no filtering predicates• Allow join columns from multiple tables to share a single compression dictionary

• Hash joins don’t have to decompress the data first• View join groups in USER_JOINGROUPS

• View shared dictionary in v$IM_SEGDICT

CREATE INMEMORY JOIN GROUP jgroup_name(order_item(ol_i_id),item(i_id));


IM Join Group Example – Cont.

SELECT ol_o_id,ol_number, ol_delivery_d, i_name, i_priceFROM order_item, itemWHERE ol_i_id = i_id and i_price < 2.00;

• Join Groups share the same compression dictionary• This allows for joins to occur on compressed values• Doesn’t need to decompress and hash the data• Join columns above are order_item.ol_i_id and item.i_id

• Tables need to be reloaded after the Join Group creation• To create the common compression dictionary, called Global Dictionary• Ensure the Global Dictionary exists by checking V$IM_SEGDICT_GD

SELECT o.object_name table_name,c.column_name column_name,gd.head_address "GD Address"

FROM user_objects o,user_tab_columns c,v$im_segdict gd

WHERE gd.objn = o.object_idAND o.object_name = c.table_nameAND gd.column_number = c.column_id;


IM Join Group Example – New 12.2 Feature


No IM

Using Bloom Filter / Join Group?

IM Join Group Example

• Finding join group usage• Need to use SQL_MONITOR - dbms_sqltune.report_sql_monitor_xml or OEM

• Query needs ‘SELECT /*+ MONITOR */’ hint• Columnar encodings leveraged = 1


Columnar Encodings

Leveraged

New SQL

• 12.1• FETCH FIRST n ROWS ONLY

• Retrieves first rows without scanning everything• Faster

• OFFSET n ROWS FETCH FIRST n ROWS ONLY• Skip some number of rows


New SQL

• 12.2 Approximate Query Processing• Used for approximate ‘count distinct’ values and adds percentile aggregation• Allows for faster processing of large data sets

• Not exact but usually within 95%+ range

• Three new parameters – alter system/session • approx_for_aggregation Default=FALSE

• Can be overridden by the next 2 parameters• If true, sets approx_for_percentile=ALL

• approx_for_count_distinct Default=FALSE• Overrides exact COUNT DISTINCT clause

• approx_for_percentile Default=NONE• Overrides MEDIAN clause (PERCENTILE_CONT)• Values can be PERCENTILE_CONT, PERCENTILE_DISC, and ALL

• Can be used without any changes to existing code • Replaces exact functions with SQL functions (next page) that return approximate results


New SQL functions in 12.2

• Approximate query functions• APPROX_COUNT_DISTINCT (Introduced in 12.1)• APPROX_COUNT_DISTINCT_DETAIL• APPROX_COUNT_DISTINCT_AGG• TO_APPROX_COUNT_DISTINCT• APPROX_MEDIAN• APPROX_PERCENTILE• APPROX_PERCENTILE_DETAIL• APPROX_PERCENTILE_AGG• TO_APPROX_PERCENTILE

• Also in 12.2, support for Materialized Views and Query Rewrite• VALIDATE_CONVERSION

• Determines if a given input value can be converted to a requested data type• Simplifies coding


Approximate SQL Example


95% accurate

Approximate SQL Example With Changing Code


Why is it exact?

Need to

set both

Approximate Percentile Example With Changing Code


99.68% accurate

12.2 Dictionary Improvements and Other New Stuff


• Object identifiers have increased from 30 bytes to 128 bytes• Such as users, roles, tables, columns, indexes, constraints, etc…

• Changed in dictionary views - instead of VARCHAR2(30), now VARCHAR2(128)• May affect your reporting

• Exceptions:• Disk groups, pluggable databases (PDBs), rollback segments, and tablespaces still 30 bytes• Names of databases are still limited to 8 bytes

• SQLPlus Improvements• HISTORY

• SET HIST[ORY] {ON | OFF | n}• SHOW HISTORY• RUN n

• SET ROWPREFETCH {1 | n} / SET LOBPREFETCH {0 | n} • SET STATEMENTC[ACHE] {0 | n}

12.2 Optimizer Changes

• New init.ora parameters• OPTIMIZER_ADAPTIVE_PLANS (Default = TRUE)

• Adaptive joins• Bitmap pruning• Parallel distribution method

• OPTIMIZER_ADAPTIVE_STATISTICS (Default = False)• SQL Plan Directives (SPDs) for query optimization• Statistics feedback (for joins only)• Adaptive dynamic sampling for parallel queries• Performance feedback

• Obsolete• OPTIMIZER_ADAPTIVE_FEATURES


12.2 Optimizer Changes

• SQL Plan Directives• Control of Auto Creation of Column Group Statistics• New DBMS_STATS preference

• AUTO_STAT_EXTENSIONS (DEFAULT=OFF)

EXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_STAT_EXTENSIONS','ON')

• Can view in DBA_STAT_EXTENSIONS

select owner,table_name,extension,extension_name

from dba_stat_extensionswhere creator = 'SYSTEM'order by owner,table_name,extension_name;


Multitenant Changes in 12.2

• Can create a hot clone of PDB• No downtime for PDB being cloned

• Uses redo then undo for all committed / uncommitted transactions

• Local undo required • Undo can now exist in PDB

• Archive logging must be enabled

• Can create a refreshable PDB (for VLDBs)• Built on top of hot clone• Golden master for snapshot clones• Automatically or manually refreshed from redo• Opened in read-only mode

• Can relocate PDBs to different CDBs online• Built on top of Refreshable PDB• Great way to load-balance


Can help maintain SLAs for

performance and availability

Multitenant Changes in 12.2

• Can have 4096 PDBs per CDB • Instead of original 252

• Can flashback a single PDB• Doesn’t have to use local undo but easier than shared undo• Can use SCN, restore point, clean restore point or guarantee restore point

• View SCNs in V$FLASHBACK_DATABASE_LOG

• https://oracle-base.com/articles/12c/multitenant-flashback-pdb-12cr2

FLASHBACK PLUGGABLE DATABASE pdb1 TO TIMESTAMP some_date;

• Data Guard now supports individual PDB-level failover• Used to be all PDBs or none• Now can set parameter ENABLED_PDBS_ON_STANDBY on standby database

• Examples – ‘*’, ‘PDB?’, ‘PDB*’, ‘-PDB1’


https://oracle-base.com/articles/12c/multitenant-flashback-pdb-12cr2

New Memory Settings At PDB Level

• If using Database Smart Flash Cache• Can set CDB resource plan to allocate memory between PDBs

• MEMORY_LIMIT – percentage that limits PDB memory usage• MEMORY_MIN – percentage guaranteed for PDB memory usage• http://docs.oracle.com/cd/E80920_01/SAGUG/exadata-storage-server-iorm.htm#SAGUG20421

• Can set INMEMORY_SIZE at PDB• Can be over-subscribed


http://docs.oracle.com/cd/E80920_01/SAGUG/exadata-storage-server-iorm.htm#SAGUG20421

12.2 Partitioning Features

• Read-only partitions• Useful for old partitions• Use READ ONLY • READ WRITE (default)• Can use CTAS or ALTER



• Convert Non-partitioned table • To a partitioned table ONLINE


UPDATE INDEXES clause is

optional. Indexes with SYS

names will be generated if not

used


• Automatic List Partitions• Requires creation of first partition• No default partitions


Multi-column List PartitionsCan only have one default partition


• Filtered Partitions for Maintenance Operations• Helps with partition pruning and data cleanup

• MOVE PARTITION• MERGE PARTITION• SPLIT PARTITION

• Can do ONLINE

• Other New Features• ‘For exchange with’ clause• Partitioned external tables• 12.2-partition-create-tables


https://docs.oracle.com/database/122/VLDBG/partition-create-tables-indexes.htm#VLDBG00301

12.2 Sharding Feature

• Sharding horizontally partitions data across independent databases• A ‘share nothing’ architecture – CPU, memory, disk• Each database is known as a shard• All shards together make up a logical database

• Called sharded database (SDB)

• Intended for custom OLTP applications that:• Have a well-defined data model • Have a data distribution strategy

• (consistent hash, range, list, or composite)

• Primarily access data using a sharding key• e.g., customer_id, account_no, or country_id


https://docs.oracle.com/database/122/ADMIN/sharding-overview

https://docs.oracle.com/database/122/ADMIN/sharding-overview.htm#ADMIN-GUID-D90D0A33-1BCB-48D8-8193-8FD1C2959371

12.2 Sharding Feature

• Benefits of Sharding• Linear scalability for performance and capacity• Eliminates single points of failure

• Nothing is shared

• Geographical distribution of data• Data is closer to consumers (e.g. Facebook)• Satisfies regulatory requirements

• Simplifies Cloud Deployment• Easy to do rolling upgrades

• Examples of Companies • Online payment systems

• Regulatory requirements

• Airline ticketing systems• Social media companies


http://www.oracle.com/technetwork/database/availability/oraclesharding-whitepaper

http://www.oracle.com/technetwork/database/availability/oraclesharding-whitepaper-3675509.pdf

Other SDB Components

• Shard Catalog• An Oracle database that centralizes management of a SDB• Supports automated shard deployment• Handles multi-shard queries• Holds master copy of duplicated table

• Shard Directors• Network listeners which route connections based on a sharding key• Connection pools can act as shard directors for pooled connections

• Global service• An extension of database services for the SDB

• Management Interfaces• GDSCTL (command-line utility) and OEM


SDB Architecture


https://docs.oracle.com/database/122/ADMIN/sharding-overview

To install, download

Oracle Database 12c Release 2 :

linuxx64_12201_database.zip

Oracle Database 12c Release 2 Global Service Manager :

linuxx64_12201_gsm.zip

https://docs.oracle.com/database/122/ADMIN/sharding-overview.htm#ADMIN-GUID-D90D0A33-1BCB-48D8-8193-8FD1C2959371

http://www.oracle.com/technetwork/database/enterprise-edition/downloads/oracle12c-linux-12201-3608234.html

http://www.oracle.com/technetwork/database/enterprise-edition/downloads/oracle12c-linux-12201-3608234.html

Summary

• Oracle 12.2 provides a lot of new features and enhancements• This presentation only touches on a few

• In-Memory virtual columns• Helps speed up analytical queries

• New approximate functions• Great if you don’t need exact answers

• PDB hot cloning • Online partitioning • Sharded database (SDB) or the ‘Horizontal database’

• Good news – it’s been around in the Cloud for quite sometime• Became available for on-premise in March 2017• Hopefully many of the bugs have been worked out

• Try it out and tell me which new feature you like best• Email me at [email protected]


www.solarwinds.com/dpa-download/

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Technology

Oracle 12.2 - My Favorite Top 5 New or Improved Features