Anthony Reina - Accelerated Value Specialist
aereina@ca.ibm.com
Performance Enhancements for DB2 V10.1
Information Management
© 2010 IBM Corporation
Information Management
IBM Software
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Information Management
Agenda :
• RUNSTATS and database statistics
improvements
• Registry variables and inexact matching for
Optimization profile
• Statistical view
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Information Management
RUNSTATS
 INDEXSAMPLE : Allows statistics collectio be done in sample mode.
–SYSTEM
–BERNOULLI
 Detailed Index Statistics default (DETAILED) now uses sampling method
starting in V10.1.
– SAMPLED DETAILED is still available for compatibility.
– UNSAMPLE option still available
 VIEW command parameter can be used for better usability.
 No need to fully qualify tables by schema name
 AUTO_SAMPLING now possible for all auto_stats collection on large
table and statiscial views
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Information Management
RUNSTATS
Implementation :
RUNSTATS Syntax
Database Config
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OPTIMIZATION PROFILE
 Selected OPT registry variables can now be set via optimization profile
 DB2_ANTIJOIN
 DB2_EXTENDED_OPTIMIZATION
 DB2_INLIST_TO_NLJN
 DB2_MINIMIZE_LISTPREFETCH
 DB2_NEW_CORR_SQ_FF
 DB2_OPT_MAX_TEMP_SIZE
 DB2_REDUCED_OPTIMIZATION
 DB2_RESOLVE_CALL_CONFLICT
 DB2_SELECTIVITY
 DB2_SELUDI_COM_BUFFER
 DB2_SORT_AFTER_TQ
 Registry variables can be set at the global and/or statement level.
If set at statement level…applied to statement defined for.
If set at global level…applied to all statements in the opt profile.
If set at both level…statement level takes precedence.
If not set…db2set setting is used.
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OPTIMIZATION PROFILE
Implementation :
Will affect
STMTPROFIL
E ID=‘S2’
Will affect
STMTPROFIL
E ID=‘S1’
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OPTIMIZATION PROFILE
Implementation :
Explain facility will reflect which registry variables are being used for a
particular statement.
It also indicates where the registry variables have been set
ie. db2set level,
Global Optimization Guideline
Statement-level Optimization Guideline
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OPTIMIZATION PROFILE
 Inexact matching used for flexible matching between compiling
statements and statement within optimization profile.
 Set at the STMTMATCH element of the OPTPROFILE via EXACT attribute.
 EXACT Attribute can be set TRUE or FALSE
If set TRUE then exact matching is enabled.
If set FALSE then inexact matching is enabled.
 INEXACT matching ignores constants, literals, parameter markers, and
host variables.
 Exceptions/Future Considerations :
– Order of column
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OPTIMIZATION PROFILE
 Exceptions/Future Considerations :
1. Order of column lists, table lists and predicate list must be the same
SELECT A,B FROM R,T WHERE A>B
Does not match :
SELECT B,A FROM T,R WHERE B<A
2. Symmetric operands must remain in the same order
A = B does not match B = A
A + B = 5 does not match B + A = 5
3. Parenthesis and other punctuation can prevent a match
4. No wildcard support
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OPTIMIZATION PROFILE
Implementation :
Will affect
STMTPROFIL
E ID=‘S2’
Will ONLY
affect
STMTPROFILE
ID=‘S1’
INEXACT Matching
is considered (ie. ?)
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OPTIMIZATION PROFILE
Implementation :
INEXACT for different clauses
INEXACT for predicate clause
INEXACT for IN list predicate clause
INEXACT in the select list
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STATVIEW
 Predicates containing complex expressions
 Column Group Statistics gathered on statistical views
 Automatic statistics collection for statistical views
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STATVIEW
 Reducing the number of statistical views
Given the DDL for the following tables
Referential Integrity Definition
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STATVIEW
 Reducing the number of statistical views
Statistics needed for the given query
Create the following views to create accurate statistics
Reduce the number of statistical views since RI exist between join columns
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Other Performance Enhancements
 Automatic enhanced query performance for common SQL statements
– Efficient hashing function to partially remove duplicates early in the
SQL processing.
– Hash join is select for a wider range of SQL queries.
– Improved cost estimates of network communication traffic
 Intrapartition parallelism improvements for optimizer to enable more
workloads to better use multi-core processors.
 ADMIN_SET_INTRA_PARALLEL (<state>) procedure
– Enables or disables intrapartition parallelism for a database appl.
– Takes effect starting with the next transaction.
– Values = YES/yes, NO/no, or NULL
– NULL value depends on INTRA_PARALLEL dbm cfg
 FP2: More efficient writing to recovery history file might result in
general speed performance improvement.
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Other Performance Enhancements
 Enhance memory sharing on large POWER7 systems by running AIX
– Potentially enhance query performance by effectively sharing
memory.
– DB2_RESOURCE_POLICY must be set to AUTOMATIC for DB2 to auto
detect hardward topology.
– DB2 assigns EDU’s to various hardware modules so that memory can
be more efficiently shared.
– Used only for POWER7 systems with 16 or more cores.
– Recommend to run performance planning/analysis to validate
performance gain.
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REFERENCE
 DB2 v10.1 Query Performance Enhancement (developerworks)
 Statement key and compilation key matching
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Information Management
Questions?
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