Oracle 12c New Features For Better Performance

Zohar Elkayam
www.realdbamagic.com
Twitter: @realmgic
Oracle 12c New Features
for Better Performance

Who am I?
• Zohar Elkayam, CTO at Brillix
• Programmer, DBA, team leader, database trainer, public
speaker, and a senior consultant for over 19 years
• Oracle ACE Associate
• Member of ilOUG – Israel Oracle User Group
• Blogger – www.realdbamagic.com and www.ilDBA.co.il
2 http://brillix.co.il

About Brillix
• We offer complete, integrated end-to-end solutions based on best-of-
breed innovations in database, security and big data technologies
• We provide complete end-to-end 24x7 expert remote database
services
• We offer professional customized on-site trainings, delivered by our
top-notch world recognized instructors
3

Some of Our Customers
http://brillix.co.il4

Agenda
•Database In Memory (column store) – 12.1.0.2
•Oracle Database Sharding – 12.2.0.1
•Optimizer and Statistics changes – 12c

Our Goal for Today
•Getting to know some of Oracle 12cR1 and 12cR2
new features around performance
•Not a lot of syntax today – mainly concepts
•Way too many slides, let’s try to catch ‘em all…

Oracle Database In-Memory
(Column Store)
12.1.0.2

What is an In Memory Database?
• In memory databases are management systems that keeps
the data in a non-persistent storage (RAM) for faster access
Examples:
• AeroSpike
• SQLite
• MemcacheDB
• Oracle TimesTen and Oracle Coherence

What is a Column Store Database?
• Column Store databases are management systems that
use data managed in a columnar structure format for better
analysis of single column data (i.e. aggregation).
Data is saved and handled as columns instead of rows.
Examples:
• Apache Cassandra
• Apache HBase
• Apache Parquet
• Sybase IQ
• HP Vertica

How Records are Organized?
• This is a logical table in RDBMS
• Its physical organization is just like the logical one: column
by column, row by row
Row 1
Row 2
Row 3
Row 4
Col 1 Col 2 Col 3 Col 4

Query Data
• When we query data, records are read at the
order they are organized in the physical structure
• Even when we query a single
column, we still need to read the
entire table and extract the column
Row 1
Row 2
Row 3
Row 4
Col 1 Col 2 Col 3 Col 4
Select Col2
From MyTable
Select *
From MyTable

How Does Column Stores Keep Data
Organization in row store Organization in column store
Select Col2
From MyTable

Row Format vs. Column Format

In Memory Option Breakthrough
• In memory option introduces a dual format database
• Tables can be accessed as row format and column format at the same
time – the Optimizer is aware to the new format so:
• OLTP continue using the old row format
• Analytic queries start using the column format

Oracle In Memory Option
•Column data is pure in memory format: it’s non-
persistent and require no logging, archiving or backup
•Data changes are simultaneously changed in both
formats so data is consistent and current
•Application code requires no changes – just turn on
and start using

In Memory Option – Good To Know
• It is Not “In Memory Database” – it’s an accelerator to the
regular database
• It is Not “Column Store Database” – column organized data
is non-persistent*
• In Memory Option requires more memory than the data you
plan to load to the memory: no LRU mechanism
• Not related to Oracle Times-Ten or Oracle Coherence

Oracle Buffer Cache and Memory Management
•Oracle buffer cache can keep data blocks in memory
for optimization
•Blocks are removed from memory based on their
usability (LRU)
•If data is smaller than available memory, we can use
Oracle 12c new features: Full Database Caching

Full Database Caching
• Full Database Caching: Implicit default and automatic mode
in which an internal calculation determines if the database
can be fully cached
• Force Full Database Caching: This mode requires the DBA
to execute the ALTER DATABASE FORCE FULL DATABASE
CACHING command
• Neither Full Database Caching nor Force Full Database
Caching forces prefetch of data into the memory

What’s new In 12cR2?
•In memory support for Active Data Guard configuration
•In memory virtual columns and expressions
•In memory FastStart
•Automatic Data Optimization Support for In-Memory
Column Store

Oracle Sharding
12.2.0.1

Scaling Databases
•Why would we want to scale our database
• Performance
• Elasticity
• Global data distribution
•Possible solutions:
• Scaling up – adding more hardware
• Scaling out – the Oracle way, using RAC
• Scaling out using sharding

What Is Sharding?
•Sharding is a way of horizontal scaling (horizontal
partitioning)
•Instead of scaling the database infrastructures, we
scale out the data itself
•Not a new concept: MongoDB, Cassandra, MySQL…
•Starting with Oracle 12.2 we can use Sharded
Database Architecture (SDA) as part of Oracle
Global Data Services (GDS) architecture

Global Data Services (GDS)

Sharded Database Architecture (SDA)
•Part of the Global Data Services (GDS) architecture
•Databases in the logical database doesn’t share any
physical resources or clusterware software
•Databases can reside in different geo-locations
•Application must be compatible with sharded behavior

Benefits of Sharding
• Linear Scalability - eliminates performance bottlenecks and makes it
possible to linearly scale performance by adding shards
• Fault Containment - Sharding is a shared nothing hardware
infrastructure that eliminates single points of failure
• Geographical Distribution of Data - store data close to its users
• Rolling Upgrades – changes to one shard at a time does not affect
other shards
• Simplicity of Cloud Deployment - supports on-premises, cloud, and
hybrid deployment models

Why RDBMS Sharding?
•Unlike NoSQL sharding, Oracle Shards still support
• Relational schemas
• ACID transactions properties and read consistency
• SQL and other programmatic interfaces
• Complex data types
• Database partitioning
• Advanced security
• High Availability features
• And more…

The Big Picture

Server A – Non-Sharded
Sharding Methods
•We can use two methods of sharding data:
• Sharded tables: data exist is one shared
• Duplicated tables: data exist in all shareds
SDB – Sharded (Logical) Database
Server
B
Server
C
Server
D
Shard 1 Shard 2 Shard 3

Example – Sharded Table Creation
CREATE SHARDED TABLE customers
( cust_id NUMBER NOT NULL
, name VARCHAR2(50)
, address VARCHAR2(250)
, region VARCHAR2(20)
, class VARCHAR2(3)
, signup DATE
CONSTRAINT cust_pk PRIMARY KEY(cust_id)
)
PARTITION BY CONSISTENT HASH (cust_id)
TABLESPACE SET ts1
PARTITIONS AUTO;

Example – Duplicated Table Creation
CREATE DUPLICATED TABLE Products
( StockNo NUMBER PRIMARY KEY
, Description VARCHAR2(20)
, Price NUMBER(6,2))
);

Sharded Table Families
•We can shard multiple tables to the same database
shard using table families
•All tables in a table family must have the same equi-
partition sharding key:
• Using Reference partitions
• Using the PARENT clause

Example – Sharded Table Family Creation (REF)
CREATE SHARDED TABLE Customers
( CustNo NUMBER NOT NULL
, Name VARCHAR2(50)
, Address VARCHAR2(250)
, CONSTRAINT RootPK PRIMARY KEY(CustNo)
)
PARTITION BY CONSISTENT HASH (CustNo)
PARTITIONS AUTO
TABLESPACE SET ts1;
CREATE SHARDED TABLE Orders
( OrderNo NUMBER NOT NULL
, CustNo NUMBER NOT NULL
, OrderDate DATE
, CONSTRAINT OrderPK PRIMARY KEY
(CustNo, OrderNo)
, CONSTRAINT CustFK FOREIGN KEY
(CustNo) REFERENCES Customers(CustNo)
)
PARTITION BY REFERENCE (CustFK);

Example – Sharded Table Family Creation
(PARENT)
CREATE SHARDED TABLE Customers
( CustNo NUMBER NOT NULL
, Name VARCHAR2(50)
, Address VARCHAR2(250)
, region VARCHAR2(20)
, class VARCHAR2(3)
, signup DATE
)
TABLESPACE SET ts1
PARTITIONS AUTO;
CREATE SHARDED TABLE Orders
( OrderNo NUMBER
, CustNo NUMBER
, OrderDate DATE
)
PARENT Customers
TABLESPACE SET ts1
PARTITIONS AUTO;

Non-Table Objects
•We can create non-table objects in the logical
databases
• Schema objects: users, roles, views, indexes, synonyms,
functions, procedures, and packages
• Non-schema objects: tablespaces, tablespace sets,
directories, and contexts
•Objects will be created on all shards

DDL Execution
• The application schema name and all objects name must be
identical on all shards
• DDL on sharded table must be done from the Shared catalog
database or using GDS command line tool (GDSCTL)
• Changes are automatically propagated to all shards
SQL> CONNECT SYS@SH_CATALOG
SQL> ALTER SESSION ENABLE SHARD DDL;
SQL> CREATE USER <app_name>...
SQL> GRANT CREATE TABLE TO <app_name>...
SQL> CREATE DUPLICATED TABLE <name>...
SQL> CREATE SHARDED TABLE <name>...
GDSCTL> sql "CREATE USER ..."
GDSCTL> sql "CREATE TABLESPACE
SET ..."

Sharding Physical Structure
•Physical data distribution based on chunks – each
chunk is one table partition
•Each chunk is located on a different tablespace
•Tablespaces are defined using tablespace sets
(tablespace templates)

Resharding and Hotspots Handling
• Adding/Removing shards or hotspot elimination requires
chunk movement (automatically or manually)
• This will generate an RMAN backup, restore and recovery
of the chunk (tablespace) in the new node. Old chunk will
be automatically removed once done.
• We can also split hotsposts using GDSCTL split command
GDSCTL> MOVE CHUNK -CHUNK 12 -SOURCE sh01 -TARGET sh12
GDSCTL> SPLIT CHUNK -CHUNK 12

Sharding High Availability
•Data replication with Data Guard is a crucial
component in SDB environment
• High availability, disaster recovery, read offloading
• Replication deployment performed fully automatically
• The logical unit of data replication is a shardgroup

High Availability Setup Example
GDSCTL> create shardcatalog -database shdard01:1521:repo
-chunks 12 -user mygdsadmin/<pwd> -sdb sharddb
-region london,Amsterdam –repl DG –sharding system
-protectmode maxavailability
...
GDSCTL> add shardgroup -shardgroup shardgrp1 -deploy_as primary
-region london
GDSCTL> add shardgroup -shardgroup shardgrp2 -deploy_as active_standby
-region london
GDSCTL> add shardgroup -shardgroup shardgrp3 -deploy_as active_standby
-region amsterdam

Session Routing (single shard)
• Application must be compatible with sharding architecture
• When connecting to the database, the application must
provide the sharding key (and super key) to the connection
• All SQL operations in this session are related to the specified
sharding key (shard)
• To work on another sharding key value, the application needs to
create a new session

Statement Routing/Cross-Shard Query
•Client connection to the Coordinator (Catalog)
Database is required
• No sharding key necessary in the connect descriptor
•Cross-shard SQL are executed via DB Link to Shards
• Partition and Shard pruning

Optimizer Changes and
Adaptive Query Optimization
12.1.0.2 + 12.2.0.1

Adaptive Query Optimization
Adaptive Query
Optimization
Adaptive Plans
Adaptive
Statistics
At compile
time
At run timeJoin
Methods
Parallel
distribution
Methods

Adaptive Execution Plans (12.1)
• Allows the Optimizer to make runtime adjustments to execution
plans and to discover additional information that can lead to
better statistics
• Good SQL execution without intervention
• Final plan decision is based on rows seen during execution
• Bad effects of skew eliminated

Adaptive Execution Plans: Join Methods
• Join method decision deferred until runtime
• Default plan is computed using available statistics
• Alternate sub-plans are pre-computed and stored in the cursor
• Statistic collectors are inserted at key points in the plan
• Final decision is based on statistics collected during execution
• Possible sub-plans are nested loop joins or hash joins and vice
versa

Displaying the Default Plan
•Explain plan command
always shows default plan
•Example shows a nested
loops join as default plan
•No statistics collector
shown in plan

Displaying the Final Plan
• After the statement has
completed use
DBMS_XPLAN.DISPLAY_CURSOR
to see the final plan
selected
• Example shows that hash
join picked at execution time
• Again the statistics collector
is not visible in the plan

Displaying Plan With +adaptive & +report Formats
• Additional information displayed on why operations are inactive can be
seen with format parameter ‘+report’

Adaptive Execution Plans In V$SQL

Dynamic Statistics (12.1  11.2.0.4)
•During compilation optimizer decides if statistics are
sufficient to generate a good plan or not
•Dynamic statistics are used to compensate for
missing, stale, or incomplete statistics
•They can be used for table scans, index access, joins
and group by
•One type of dynamic statistics is dynamic sampling

Dynamic Statistics
• Dynamic sampling has a
new level 11(AUTO)
• Decision to use dynamic
sampling depends on the
complexity of predicate,
existing statistics and total
execution time
• Dynamic statistics shared
among queries

Adaptive Statistics/Statistics Feedback
Re-optimization Pre 12c:
• During execution optimizer estimates are compared to execution statistics
• If statistics vary significantly then a new plan will be chosen for subsequent
executions based on execution statistics
• Re-optimization uses statistics gathered from previous executions
Re-optimization in 12c
• Join statistics are also monitored
• Works with adaptive cursor sharing for statement with binds
• New Column in V$SQL IS_REOPTIMIZABLE
• Information found at execution time is persisted as SQL Plan Directives

Statistics Feedback

Re-optimization – indicator in V$SQL
•New column in V$SQL: IS_REOPTIMIZABLE
•Indicates that the statement will be re-parsed on the
next execution

More Optimizer Changes…
•Adaptive Statistics/Statistics Feedback (12.1)
•Concurrent Execution of UNION and UNION ALL
Branches (12.1)
•Cost-Based OR Expansion Transformation (12.2)
•Enhanced Join Elimination (12.2)
•Approximate Query Processing (12.1 + 12.2)

Statistics
12.1.0.2 + 12.2.0.1

Histograms
• Histograms tell the Optimizer about the data distribution in a
Column for better cardinality estimations
• Default create histogram on any column that has been used
in the WHERE clause or GROUP BY of a statement AND has a
data skew
• Oracle 12c changes histograms methods:
• Top-Frequency (new)
• Height balanced (obsolete)
• Hybrid (new)

Histograms: Top Frequency
• Traditionally a frequency histogram is only created if NDV < 254
• But if a small number of values occupies most of the rows
(>99% rows), creating a frequency histograms on that small set
of values is very useful even though NDV is greater than 254
• Ignores the unpopular values to create a better quality histogram
for popular values
• Built using the same technique used for frequency histograms
• Only created with AUTO_SAMPLE_SIZE

Top Frequency Histogram Example
• Table
PRODUCT_SALES
contains information on
Christmas ornament
sales
• It has 1.78 million rows
• There are 620 distinct
TIME_IDs
• But 99.9% of the rows
have less than 254
distinct TIME_IDs
TIME_ID column perfect
candidate for top-frequency
histogram

Height Balanced Histograms (obsolete)
•A height balanced histogram is created if the number
of distinct values in a column (NDV) is greater than
254 values. This is now obsolete.
Height balanced histogram

Hybrid Histograms
•Hybrid histogram is created if the number of distinct
values in a column (NDV) is greater than 254 values
but uses actual frequencies of bucket endpoints
Hybrid histogram

Hybrid Histograms
• Similar to height balanced histogram as created if the NDV
>254
• Store the actual frequencies of bucket endpoints in
histograms
• No values are allowed to spill over multiple buckets
• More endpoint values can be squeezed in a histogram
• Achieves the same effect as increasing the # of buckets
• Only created with AUTO_SAMPLE_SIZE

Height-balanced versus Hybrid Histogram
Oracle Database 11g Oracle Database 12c

Session Private Statistics for GTT’s
• GTT’s had only one set of statistics that were shared among all
sessions even though the table could contain different data in different
sessions
• Starting Oracle 12c, GTT’s now have session private statistics, which
is a different set of statistics for each session
• Queries against GTT use statistics from their own session
• Improves the performance and manageability of GTT’s
• Reduces the possibility of errors in the cardinality estimates for GTT’s
and ensures that the optimizer has the data to generate optimal
execution plans

Online Statistics Gathering for Bulk Loads
• Table statistics are gathered automatically during bulk
loads:
• CREATE TABLE AS SELECT
• INSERT INTO … SELECT
• Improved performance: avoids an additional table scan to
gather table statistics
• Improved manageability: no user intervention is required to
gather statistics after a bulk load
• To disable use hint: NO_GATHER_OPTIMIZER_STATISTICS

Optimizer Statistics Advisor (12.2)
• Optimizer Statistics Advisor is built-in diagnostic software that
analyzes the quality of statistics and statistics-related tasks

Optimizer Statistics Advisor (12.2)
•The advisor automatically diagnoses problems in the
existing practices for gathering statistics
•The advisor does not gather a new or alternative set of
optimizer statistics
•The output of the advisor is a report of findings and
recommendations

What Can Go Wrong With Statistic Gathering?
•Legacy scripts may not keep pace with new best
practices, which can change from release to release
•Resources are wasted on unnecessary statistics
gathering
•Statistics can sometimes be missing, stale, or incorrect
•Automatic statistics gathering jobs do not guarantee
accurate and up-to-date statistics

Optimizer Statistics Advisor: Output Example
----------------------------------------------------------------------------------------------------
GENERAL INFORMATION
-------------------------------------------------------------------------------
Task Name : MY_TASK
Execution Name : EXEC_52
Created : 12-07-16 11:31:40
Last Modified : 12-07-16 11:32:37
-------------------------------------------------------------------------------
SUMMARY
-------------------------------------------------------------------------------
For execution EXEC_52 of task MY_TASK, the Statistics Advisor has 6
finding(s). The findings are related to the following rules: USECONCURRENT,
AVOIDSETPROCEDURES, USEDEFAULTPARAMS, USEGATHERSCHEMASTATS, AVOIDSTALESTATS,
UNLOCKNONVOLATILETABLE. Please refer to the finding section for detailed
information.
-------------------------------------------------------------------------------
FINDINGS
-------------------------------------------------------------------------------
...

Optimizer Statistics Advisor: Output Example (2)
-------------------------------------------------------------------------------
FINDINGS
-------------------------------------------------------------------------------
Rule Name: UseConcurrent
Rule Description: Use Concurrent preference for Statistics Collection
Finding: The CONCURRENT preference is not used.
Recommendation: Set the CONCURRENT preference.
Example:
dbms_stats.set_global_prefs('CONCURRENT', 'ALL');
Rationale: The system's condition satisfies the use of concurrent statistics
gathering. Using CONCURRENT increases the efficiency of statistics
gathering.
----------------------------------------------------
...

More Statistics Features
•Concurrent statistics gathering (12.1)
•Automatic Column Group Detection for extended
statistics (12.2)
•Enhancements to Incremental Statistics
•Enhancements to System Statistics
•More…

Summary
•We talked about DBIM and the column store solution
•We overviewed the new Sharding solution
•We looked into new Optimizer and Statistics changes
•12c has a lot to offer us, try it – use it!
•12cR2 release date for on-prem usage: March 15, 2017
(March 1st for Exadata)

What Did We NOT Talk About
•SQL Plan Management framework
• Automatic Plan Evolution
• Enhanced Auto Capture
• Capture from AWR Repository
•Indexing, Partitioning, and many other performance
related new features…

Thank You
Zohar Elkayam
twitter: @realmgic
Zohar@Brillix.co.il
www.realdbamagic.com

Oracle 12c New Features For Better Performance

Oracle 12c New Features For Better Performance

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