SAGE Computing Services Customised Oracle Training Workshops and Consulting Customised Oracle Training Workshops and Consulting Bind Peeking – The Endless Tuning Nightmare Penny Cookson Managing Director and Principal Consultant Working with Oracle products since 1987 Oracle Magazine Educator of the Year 2004 Oracle ACE www.sagecomputing.com.au [email protected]
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SAGE Computing ServicesCustomised Oracle Training Workshops and ConsultingCustomised Oracle Training Workshops and Consulting
Statements with bind variables (+histograms) are bind itisensitive
The first time you execute a statement with different selectivity it uses the original plan
The second time it changes the plan and become bind awareThe second time it changes the plan and become bind aware
New values will use a plan for the appropriate selectivity range
Be careful when statements become invalidated by:-Gathering statisticsFlushing the shared poolRestarting the databaseOr when they are aged out
Adaptive Cursors Functionality
Adaptive Cursors 11 1 0 6Adaptive Cursors 11.1.0.6Bind variable with Equality and HistogramNot for range conditionsNot for range conditions
Adaptive Cursors 11.1.0.7Bind variable with Equality and HistogramBind variable with Equality and HistogramRange conditionsDo Not Support LIKEDo Not Support LIKE
Future?LIKELIKESELECT /*+ HINT TO MAKE IT BIND AWARE */
Gathering Statisticsg
E l CBO “M k th t ti ti l l ”Early CBO: “Make sure you gather statistics regularly”
Later CBO: “Don’t gather statistics unless data patternschange”change
BUTIf you have new majority values you need to recreate thehistogram
SQL Plan ManagementManual captureDBMS_SPM.LOAD_PLANS_FROM_SQLSET
DBMS SPM.LOAD PLANS FROM CURSOR CACHE
Auto capture of repeatable statementsOPTIMIZER_CAPTURE_SQL_PLAN_BASELINE = TRUE
DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE
B li
SQL Management Base
M l l d/ t f l Baseline = (Stored and Accepted plans)
Manual load/accept of new planDBMS_SPM.LOAD_PLANS_FROM_SQLSET
DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE
SQL Tuning Advisor identifies new plan SQL*Profile accepted
Auto accept of new plan (if it performs better)
N Pl
plan – SQL Profile accepted (if it performs better)DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE
New Plan identified during execution
Stored not accepted
SQL Plan Management – Binds
• Will not automatically handle adaptive cursors• New plan identified on first execution• New plan identified on first execution• New plan recorded as not accepted• Plan will not evolve• All bind variable values use same baseline plan• Plans show as not bind sensitive or aware
SQL Plan Management – Binds
SQL Plan Management – Binds
SQL Plan Management – Binds
Force Acceptance of the plan
SAGE Computing ServicesCustomised Oracle Training Workshops and ConsultingCustomised Oracle Training Workshops and Consulting