FAQ: SQL Plan Management (SPM) Frequently Asked Questions
(Doc ID 1524658.1)
Last updated on MARCH 28, 2019
Applies to:Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
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Information in this document applies to any platform.
This document addresses a number of Frequently Asked Questions for SQL Plan Management (SPM).
These Questions and Answers were generated from the Q&A Session for "How to achieve Plan Stability on 11g with SQL Plan Management (SPM)" Webcast. The recording for this webcast can be accessed in the following document:
SQL plan management is a preventative mechanism that can records and evaluate the execution plans of SQL statements over time. This mechanism can build a SQL plan baseline, which is a set of accepted plans for a SQL statement. The accepted plans have been proven to perform well.
Oracle® Database Performance Tuning Guide
11g Release 2 (11.2)
Part Number E16638-06
Chapter 15 Using SQL Plan Management
Chapter 20 Using Plan Stability
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In this Document
|Ask Questions, Get Help, And Share Your Experiences With This Article|
|Questions and Answers|
|What is the difference between a SPM Baseline, a SQL Profile and a SQL_PATCH?|
|Can there be Multiple baselines?|
|Is there a feature which allows partitioning a baseline for multiple user profiles, for example one for application, one default and another for selected end users?|
|I ran my SQL with optimizer_capture_sql_plan_baselines = true but I do not see a baseline in dba_sql_plan_baselines?|
|If I have a SPM baseline, how do I find out what SQL_ID it relates to?|
|How can I display the plans for a SQL statement recorded in a SPM baseline?|
|Do I need to change my statistics gathering routine having implemented SPM Baselines?|
|How do I move SPM Baselines between databases?|
|How do SPM Baselines integrate with Adaptive Features?|
|How do SPM Baselines interact with the Oracle Database In-Memory Option?|
|What is the order of precedence for Baselines, SQL profiles, Outlines, Hints etc?|
|How does SPM decide between the same SQL statement called by two different database users, referencing two different tables with the same name?|
|How can I Monitor Plan Evolution?|
|How are Adaptive Plans evolved?|
|How does a DBA decide which plans to accept and enable?|
|What is the recommended method for plan capture?|
|Is it good to set auto capture to true right after an upgrade of the Database?|
|What if the first captured plan is not the most optimal?|
|How can plans be migrated from Oracle 9i?|
|Is it possible to load plans from the AWR into SPM?|
|Is it possible to upload an existing baseline or manually create a baseline?|
|If a baseline is imported from a "test" database into a "production" database do environment variables that must be set to the same values (e.g. optimizer_mode)?|
|Why doesn't the view, DBA_SQL_PLAN_BASELINES, display execution statistics? Columns, such as ELAPSED_TIME and CPU_TIME, are zero.|
|Performance and Footprint|
|What is the performance impact of setting optimizer_capture_sql_plan_baselines on a production system?|
|How can you calculate additional disk space in the sysaux tablespace for spm?|
|How can you verify the performance of different accepted plans stored in a baseline verses non accepted plans?|
|Does capturing and use of SPM baselines degrade the database performance?|
|Troubleshooting SPM Baseline Issues|
|What are the known issues with SPM ?|
|What should I collect to diagnose issues where an SPM baseline is not used?|
|Discuss SQL Plan Management (SPM)|