Oracle 12.2 - My Favorite Top 5 New or Improved Features

Oracle 12.2 – My Favorite Top Five
New or Improved Features
Janis 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?

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 Cache
Analytics in In-Memory
Column Store

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_price
FROM order_item, item
WHERE 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_id
AND o.object_name = c.table_name
AND 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_extensions
where 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’

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

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 Partitions
Can 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

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

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

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

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 janis.griffin@solarwinds.com

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Oracle 12.2 - My Favorite Top 5 New or Improved Features

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Oracle 12.2 - My Favorite Top 5 New or Improved Features