Outlines Profiles and SQL Baselines

8/13/2019 Outlines Profiles and SQL Baselines

http://slidepdf.com/reader/full/outlines-profiles-and-sql-baselines 1/44

Outlines, Profiles and SQL Plan

BaselinesFrank Bommarito



Overview

• Optimizer Ranges• Outlines and Profiles• SQL Plan Baselines• Conclusion



Introduction

• Profiles and Outlines are used to correct specificSQL statement

• Profiles and Outlines work on SQL that has already

run and is deemed to be “poor performing”• SQL Plan Baselines capture good times to prevent

poor performing SQL.

• All are used to make a good – predictable system.



Optimizer Ranges

• The Extremes• Optimizer Flexibility• Plan Stability



The Extremes

• Optimizer Flexibility• Plan Stability• Default optimizer does a pretty good job on most SQL.• There are always some exceptions – and – often these

are not measured in seconds – sometimes in “days”• Setup the database to where most SQL is good• OLTP lean toward Plan Stability

• DW lean toward Optimizer Flexibility



Optimizer Flexibility

• Give the optimizer as much information as possible• Use histograms where data skews are possible• Generate statistics frequently

• Use dynamic sampling on “load” tables• Start with default settings and adjust only if required



Plan Stability

• Implement more stringent initialization parameters• Limit or eliminate histograms• Avoid bind variable peeking issues

• Port statistics with objects through the developmentcycle.• Reduce the impact of larger production machines (CPU

and Memory)• Execute – infrequent statistics gathering and always

store base lines statistics



Plan Stability

• Plan stability prevents certain database environmentchanges from affecting the performance characteristicsof applications. Such changes include changes inoptimizer statistics, changes to the optimizer modesettings, and changes to parameters affecting the sizesof memory structures, such as SORT_AREA_SIZE andBITMAP_MERGE_AREA_SIZE. Plan stability is mostuseful when you cannot risk any performance changes inan application.



What is an Outline – and – Profile?

• Outlines: – An outline is a stored execution path for a specific

SQL statement.

• Profiles – Enhanced database statistics for a specific SQL

statement.

• SQL Plan Baselines are shown later – In effect – a combination of outlines and profiles withintelligence.



When to use Outlines and Profiles?

• Plan Stability• Ensure that performance stays consistent between

upgrades (Database and/or application)

• Benefits of cost based optimizer with predictability ofrule based optimizer.

• Allows for tuning without changing SQL or init.ora

parameters.• Tuning of 3 rd party applications



When not to use Outlines and Profiles?

• When Oracle parameters prevent usage• When too many SQL statements need manual

tuning

• When a needed hint is not supported• When it is easy to access the application• This is a reactive tuning method – do not use if

trying to be proactive.



How to use?

• Must have privileges – CREATE ANY OUTLINE (DROP/ALTER) – CREATE ANY PROFILE (DROP/ALTER)

• Need to active usage – ALTER SYSTEM/SESSION SET … – USE_STORED_OUTLINES=Category – SQLTUNE_CATEGORY=Category



How to use?

• Need to clear active SQL memory – ALTER SYSTEM FLUSH SHARED POOL;

• Need to persist usage on reboot

– Create trigger <trgname> after startup on database…



How to use?

create or replace trigger use_outln_<cat> after startupon database

begin

execute immediate 'alter system setuse_stored_outlines=<cat>';

end; /



Where are these stored?

• Outlines – Public – outln user – ol$, ol$hints, ol$nodes tables – Private – Pre-10g – personal schema – 10g and

above – system schema – DBA_OUTLINES• Profiles

– SQL$ and SQL$OBJ tables – DBA_SQL_PROFILES



How to create one? - Outline

• alter system flush shared_pool;• alter system/session set create_stored_outlines=<cat>;

• -- Run SQL through the application.

• alter system/session set create_stored_outlines=FALSE;

• alter system set use_stored_outlines=<cat>;



How to create one? - Outline

• Create outline for category <x> onSelect * from dual;

• Often created within a “temporary” environmentAlter session set optimizer_mode=rule;Create outline <name> for category AOUG onSelect …;



What if I need a hint?

• dbms_outln.edit• Outln_switch.sql• Both work by manipulating the base tables.

Outln_switch can work on private or public tables.



What if I need a hint?

Create outline AOUG_base for category AOUG onSelect * from dual;Create outline AOUG_hinted for category AOUG onSelect /*+ full(dual) */ from dual;Call this script (put in a SQL called outln_switch.sql)@@outln_switch AOUG_HINTED AOUG_BASE



Outln_switch.sql

• This is also in the paper – along with dbms_outln.editexamples:define HINTSQL=&1define ORIGINALSQL=&2

UPDATE OUTLN.OL$HINTSSET OL_NAME=DECODE(OL_NAME,'&&HINTSQL','&&ORIGINALSQL','&&ORIGINAL

SQL','&&HINTSQL')

WHERE OL_NAME IN ('&&ORIGINALSQL','&&HINTSQL');DROP OUTLINE &&HINTSQL;



How to create one? – Profile

• Oracle OEM• DBMS_SQLTUNE• From an actual SQL statement

• From an AWR report• Paper for this presentation has specific examples• Running the DBMS_SQLTUNE does not guarantee

a fix – but – is very easy to use and often fixes.



Is it used? - Outline

• At the system level:select count(*),used from dba_outlines group by

used;COUNT(*) USED

---------- ------18 UNUSED

109 USED




Exec dbms_outln.clear_used(‘x’);Where “X” is the name of an outline.

• V$SQL – Outline_catgory, Outline_SID




• Explain Plan Results:select * from table(dbms_xplan.display());Blah

Note-----

- outline "AOUG_OUTLINE" used for thisstatement



Is it used? - Profile

• Explain Plan Results:select * from table(dbms_xplan.display());Blah – Blah - BlahNote-----

- SQL profile "SYS_SQLPROF_0146077cbd7f0000" usedfor this statement



Activate/De-Activate - Outlines• alter system/session set use_stored_outlines=FALSE;• Drop outline xyz;• Alter system flush shared_pool;• Cursor_sharing=force• Change SQL statementSelect * from dualIs the same asSelect * from dualBut –

Select dummy from dualis different



Activate/De-Activate - Profile

dbms_outln.EXACT_TEXT_SIGNATURES can ensurethat an exact match is required

ALTER OUTLINE outline_name CHANGECATEGORY TO not_used_now;alter system/session set sqltune_category=FALSE;



Activate/De-Activate - Profile

declarebegindbms_sqltune.drop_sql_profile(name =>

'SYS_SQLPROF_070515143928038');end;

/



Migrate - Outlines

• $ exp owner=outln file=outlntables=ol$,ol$hints,ol$nodes query=‘wherecategory=“<cat>”’ username=outln@test

• Prod> delete outln.ol$;• Prod> delete outln.ol$hints;• Prod> delete outln.ol$nodes;



Migrate - Outlines

• Prod$ imp full=y ignore=y file=outln• Prod> exec dbms_outln.clear_used;• Prod> alter system flush shared_pool;



Migrate - Profiles

# In testdbms_sqltune.create_stgtab_sqlprof('AOUG_PROFILES','AOUG');

dbms_sqltune.pack_stgtab_sqlprof(STAGING_TABLE_NAME=>

'AOUG_PROFILES',STAGING_SCHEMA_OWNER=>'AOUG');$ exp tables=AOUG.AOUG_profiles$ scp expdat.dmp Prod_Host:expdat.dmp

$ imp full=y ignore=y



Migrate - Profiles

dbms_sqltune.unpack_stgtab_sqlprof(PROFILE_NAME=>'%',PROFILE_CATEGORY=>'%', REPLACE=>TRUE,STAGING_TABLE_NAME=>'AOUG_PROFILES',STAGING_SCHEMA_OWNER=>'AOUG');



Pros/Cons

• Pros – Allows tuning of SQL that is not changeable – Provides “plan stability” – Allows development to production to be predictable – Gives all of the cost-based optimizer advantages with

the rule-based optimizer predictability. – Can reduce or eliminate statistics jobs

– Multiple outlines categories can be used to separateOLTP and BATCH.



Pros/Cons

• Pros – Easy to use – Easy to implement

– Supported by all known third-party applications



Pros/Cons

• Cons – Does not allow for column level variations for plans. – Requires maintenance when the application changes

– Can be disabled without knowledge – Requires “trespassing” into the application – Outlines require sophisticated tuning knowledge



SQL Plan Baselines – What is it?

• SQL Plan Baselines is a new feature with release 11of Oracle.• Used “safe” – or – “trusted” plans

• Captures new plans for later analysis• Captures can be manual or automatic• Single repository for Profiles and Outlines



How to enable?

• OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES – For automatic capturing

• Usage of DBMS_SPM package

– For manual capturing and validation• OPTIMIZER_USE_SQL_PLAN_BASELINES

– To enable usage



Manual Loading• Plans can be loaded from AWR reports and/or the SQL cursor

cache.DECLAREv_sql_plan pls_integer;BEGIN

v_sql_plans :=DBMS_SPM.LOAD_PLANS_FROM_SQLSET(sqlset_name =>'AOUG_SET');

v_sql_plans :=DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE(

sql_id => '99twu5t2dn5xd');END;



Validating PlansDBA_SQL_PLAN_BASELINES (SQL_HANDLE)

SET SERVEROUTPUT ONSET LONG 10000DECLARE

v_report clob;BEGIN

v_report :=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(sql_handle =>'SYS_SQL_593bc74fca8e6738');DBMS_OUTPUT.PUT_LINE(v_report);

END;



View an explain plan from a baseline

select * from table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SYS_SQL_209d10fabbedc741',format=>'basic'));



MigrateDBMS_SPM.CREATE_STGTAB_BASELINE(table_name =>

'AOUG_SPM');DECLAREv_plans number;BEGIN

v_plans := DBMS_SPM.PACK_STGTAB_BASELINE(table_name =>'AOUG_SPM',• enabled => 'yes');END;/



Migrate$ exp tables=AOUG_SPM$ scp expdat.dmp Prod_Host:$ On Prod Host – imp full=yDECLAREv_plans number;

BEGINv_plans := DBMS_SPM.UNPACK_STGTAB_BASELINE(table_name=> 'AOUG_SPM');

END;/



Conclusion

• Usage of optimizer features for plan stabilityprovides a powerful and effective means to takecontrol of an application. As with any otherdatabase utility, ensure that there is a completeunderstanding and setting of expectations prior toimplementation.



Questions

• Frank Bommarito• DBA Knowledge, Inc.• [email protected]

• http://www.dbaknow.com

?

Documents

Outlines Profiles and SQL Baselines