My Experience Using Oracle SQL Plan Baselines 11g/12c

My Experience Using SQL Plan Baselines
Nelson Calero
August 2014
OTN Latin America Tour

About me
•Database Consultant at Pythian
•Computer Engineer
•Oracle Certified Professional DBA 10g/11g
•Working with Oracle tools and Linux environments since 1996
•DBA Oracle (since 2001) & MySQL (since 2005)
•Oracle University Instructor
•Co-founder and President of the Oracle user Group of Uruguay
•LAOUC Director of events
•Blogger
•Frequent speaker: Oracle Open World, Collaborate, OTN Tour, JIAP, MySQL/NoSQL conferences
http://www.linkedin.com/in/ncalero @ncalerouy
2 © 2014 Pythian Confidential

Pythianoverview
•17 Years of data infrastructure management consulting
•170+ Top brands
•10000+ Systems under management
•Over 200 DBAs in 28 countries
•Top 5% of DBA work force, 9 Oracle ACEs, 4 Microsoft MVPs
•Oracle, Microsoft, MySQL, Netezza, Hadoop, MongoDB, Oracle Apps, Enterprise Infrastructure

Why SQL Plan Management?
•Oracle has several functionalities to help troubleshoot performance of SQL
•There is a lot of information online, official and by the community
–https://blogs.oracle.com/optimizer/is the Optimizer Team!
–OTN Virtual Technology summit lab –Create and evolve a Baseline: http://www.oracle.com/technetwork/articles/database/create-sql-plan- baseline-2237506.html
Share my experience using it on production environments
•RAC and single instance
•Closed source applications (Black Box)
•1000+ users, 40+ concurrent

Today’s topics
•What is SQL Plan Management?
•Simple example
–SQL matching
–Plan matching
–New plan generation
–Helper scripts
•Evolution on 11g / 12c
•Challenges
•Troubleshooting
•Daily management
–11g suggested approach

Introduction to SQL Plan Management
•SQL Plan Management is a new feature of Oracle 11.1 with no extra cost, available on Enterprise edition, enabled by default.
•The Oracle Optimizer is able to use only well-known execution plans, avoiding the usage of others plans we know inferior performance (regression).
What
Why
How

Changes in SQL plan execution can lead to worse execution times, and can impact system performance. It can be caused from a variety of reasons:
–Optimizer version, statistics, and parameters
–Structural objects changes (datatype, indexes, partitions)
–System settings
–System growth (skewed data, concurrency)
–And many more. See additional reason here: http://jonathanlewis.wordpress.com/2013/12/23/plan-changes/
Oracle Database already has several ways to control plan execution that works at different stages in the cost based Optimizer:
•Stored Outlines (deprecated in 11.1)
•SQL Profiles: adds statistics to the plan evaluation phase of the Optimizer (DBMS_SQLTUNE)
•SQL Hints: forces the optimizer to follow a specific path/action
What
Why
How

•Baselines are new objects stored on SYSAUX tablespace(SMB area)
•Each SQL statement can have many baselines
•Only enabledand acceptedplans are used
•Fixed plans take precedence, and no new plans are auto added
•Stages: plan load –plan selection –plan evolution
•New evolve advisor autotaskin 12c
•SQL needs to run more than once to be considered
•Baselines are global -not per schema
Initialization parameters
•OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES (Default: FALSE)
•OPTIMIZER_USE_SQL_PLAN_BASELINES (Default: TRUE)
What
Why
How

Introduction to SQL Plan Management -How
Old history
SQL is issued
Execution plan is generated
SQL is executed
Oracle Cost Based Optimizer (CBO)
Before 11g

Baselines are the last step evaluated by the Oracle Optimizer: if an enabledand acceptedplan for the statement exists, it will be used, maybe discarding the already generated plan.
SQL is issued
Execution plan is generated
SQL is executed
Since 11g

http://docs.oracle.com/database/121/TGSQL/tgsql_spm.htm#TGSQL626
Since 11g

SPM example –setup
SQL*Plus: Release 11.2.0.3.0 Production on Thu Aug 7 23:46:48 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 -64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> create table pp(n number, c varchar2(100));
Table created.
SQL> insert into pp select rownum, object_idfrom dba_objectswhere rownum< 100;
99 rows created.
SQL> create index pp_idxon pp(n);
Index created.
SQL> exec dbms_stats.gather_table_stats(user, ‘PP');
PL/SQL procedure successfully completed.

SPM example –capture SQL execution
SQL> alter session set optimizer_capture_sql_plan_baselines= TRUE;
Session altered.
SQL> varn number;
SQL> exec :n := 1;
SQL> select * from pp where n=:n;
N C
------------------------------------------------------------------------
1 20
SQL> /
N C
------------------------------------------------------------------------
1 20
SQL> alter session set optimizer_capture_sql_plan_baselines= FALSE;
Session altered.

SPM example –SQL and baseline matching
select signature, sql_handle, plan_name, enabled, accepted, fixed, sql_text
from dba_sql_plan_baselines;
SIGNATURE SQL_HANDLE PLAN_NAME ENA ACC FIX SQL_TEXT
--------------------------------------------------------------------------------------------------
1245871306398155660SQL_114a395a2db6c38c SQL_PLAN_12kjtb8qvdhwc8a71e415 YES YESNO select * from pp
select sql_id, exact_matching_signature, sql_text
from v$sql
where sql_textlike 'select * from pp %';
SQL_IDEXACT_MATCHING_SIGNATURE SQL_TEXT
-------------------------------------------------------------------
0a14b3yhux0401245871306398155660select * from pp where n=:n

SPM example –SQL and baseline matching
Our Baseline:
select signature, plan_namefrom dba_sql_plan_baselines;
SIGNATURE PLAN_NAME
------------------------------------------
1245871306398155660 SQL_114a395a2db6c38c
select * from pp where n=:n;
select * from pp where n=2;
select * from pp where n=1;
select sql_id, exact_matching_signature, force_matching_signature, sql_text
from v$sql
where sql_textlike 'select * from pp %';
SQL_IDEXACT_MATCHING_SIGNATURE FORCE_MATCHING_SIGNATURE SQL_TEXT
-------------------------------------------------------------------------------------------
D387kpdvh4anb 11466572521187337874 15110712337079575277 select * from pp where n=2
0a14b3yhux04012458713063981556601245871306398155660 select * from pp where n=:n
86svufrd72xqg14183734311806369169 15110712337079575277select * from pp where n=1

SPM example –plan from last run in SGA
SQL> select * from table(dbms_xplan.display_cursor);
SQL_ID0a14b3yhux040, child number 1
-------------------------------------
select * from pp where n=:n
Plan hash value: 2547524127
--------------------------------------------------------------------------------------
| Id | Operation| Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT||| | 2 (100)| |
| 1 | TABLE ACCESS BY INDEX ROWID| PP |1 | 6 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN| PP_IDX |1 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -access("N"=:N)
Note
-SQL plan baseline SQL_PLAN_12kjtb8qvdhwcdeb317bfused for this statement

SPM example –hints/plan used by Baseline
SQL> select * from table(dbms_xplan.display_sql_plan_baseline(
plan_name=> 'SQL_PLAN_12kjtb8qvdhwcdeb317bf', format => 'OUTLINE'));
--------------------------------------------------------------------------------
SQL handle: SQL_114a395a2db6c38c
SQL text: select * from pp where n=:n
--------------------------------------------------------------------------------
Plan name: SQL_PLAN_12kjtb8qvdhwcdeb317bfPlanid: 3736278975
Enabled: YESFixed: NOAccepted: YESOrigin: AUTO-CAPTURE
--------------------------------------------------------------------------------
Outline Data from SMB:
/*+
BEGIN_OUTLINE_DATA
INDEX_RS_ASC(@"SEL$1" "PP"@"SEL$1" ("PP"."N"))
OUTLINE_LEAF(@"SEL$1")
ALL_ROWS
DB_VERSION('11.2.0.3')
OPTIMIZER_FEATURES_ENABLE('11.2.0.3')
IGNORE_OPTIM_EMBEDDED_HINTS
END_OUTLINE_DATA
*/
17
Where is the
Plan hash value?
2547524127
© 2014 Pythian Confidential

SPM example –view definition
select text from dba_viewswhere view_name='DBA_SQL_PLAN_BASELINES';
SELECT /*+ dynamic_sampling(3) */
so.signature,
st.sql_handle,
...
DECODE(BITAND(so.flags, 1), 1, 'YES', 'NO'), --enabled
DECODE(BITAND(so.flags, 2), 2, 'YES', 'NO'), --accepted
...
FROM
sqlobj$ so,
sqlobj$auxdataad,
sql$textst
WHERE
so.signature= st.signatureAND
ad.signature= st.signatureAND
so.signature= ad.signatureAND
so.plan_id= ad.plan_idAND
so.obj_type= 2 AND
ad.obj_type= 2

SPM example –similar now including PHV2
SELECT /*+ dynamic_sampling(3) */ so.signature, so.name plan_name,
DECODE(BITAND(so.flags, 1), 1, 'YES', 'NO') enabled,
DECODE(BITAND(so.flags, 2), 2, 'YES', 'NO') accepted,
so.plan_idphv2
FROM
sqlobj$ so,
sqlobj$auxdataad,
sql$textst
WHERE
so.signature= st.signatureAND
ad.signature= st.signatureAND
so.signature= ad.signatureAND
so.plan_id= ad.plan_idAND
so.obj_type= 2 AND
ad.obj_type= 2;
SIGNATURE PLAN_NAME ENA ACC PHV2
-------------------------------------------------------------------
1245871306398155660 SQL_PLAN_12kjtb8qvdhwc8a71e415 YES YES2322719765

SPM example –SQL matching plan number
col phv2 for 9999999999
SELECT p.sql_id, p.plan_hash_value, p.child_number, x.phv2
FROM v$sql_planp
,xmltable('for $iin /other_xml/info where $i/@type eq"plan_hash_2" return $i'
passing xmltype(p.other_xml) columns phv2 number path '/') x
WHERE p.sql_id= '0a14b3yhux040'
and p.other_xmlis not null;
SQL_IDPLAN_HASH_VALUE CHILD_NUMBER PHV2
------------------------------------------------------------
0a14b3yhux040 29329474960 2322719765
Our previous result from the almost similar to DBA_SQL_PLAN_BASELINES:
SIGNATURE PLAN_NAME ENA ACC PHV2
-------------------------------------------------------------------
1245871306398155660 SQL_PLAN_12kjtb8qvdhwc8a71e415 YES YES2322719765

•Important attributes of a baseline (DBA_SQL_PLAN_BASELINES):
•ENABLED –this can be used if accepted
•ACCEPTED –this can be used if enabled
•FIXED –use this as preferred–no evolution
•PARSING_SCHEMA_NAME
•ADAPTIVE –new in 12c
•Purging policy –weekly autotaskto delete unused plans. Parameters:
•SPACE_BUDGET_PERCENT -% used -default 10 -alert.log
•PLAN_RETENTION_WEEKS –to delete non used plans -default 53
•DBA_SQL_MANAGEMENT_CONFIG view
•Can be changed using DBMS_SPM.CONFIGURE

SQL Plan Management objects
SPM included in the SQL Management Base (SMB).
SBM also has:
–Statement log –SQL$
–Baselines plan history (12c) -SQLOBJ$PLAN
–SQL plan baselines
•DBA_SQL_PLAN_BASELINES view
•DBMS_SPM package
–SQL profiles
•DBA_SQL_PROFILES view
•DBMS_SQLTUNE / DBMS_AUTO_SQLTUNE package

When to use SPM
•Just another tool for performance management
•Database upgrade: known plans can be captured/exported/imported
•Third party applications: can include exported baselines to guarantee known behaviour
What is automated by advisors?
•SQL Tuning Advisor (Tuning pack licence!) -SYS_AUTO_SQL_TUNING_TASK
–Create profiles (and baseline if present) if ACCEPT_SQL_PROFILES parameter is TRUE
–Manually using DBMS_AUTO_SQLTUNE.ACCEPT_SQL_PROFILE
•Evolve advisor on 12c -SYS_AUTO_SPM_EVOLVE_TASK(more later)
–parameter ACCEPT_PLANS defaults TRUE
All good things without extra effort?
•Forces us to follow the evolution of SQLs who uses it
–blindly trust is not a good idea
•Needs a good understanding to explain why an existing baseline is not used

More than just plan selection
Plan load/capture and evolution
Creating new Baselines manually:
•capture plans being in use by the instance
–OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=TRUE
•load plans from cursor cache
–DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE
•load plans from SQL tuning set -Oracle Tuning Pack license
–DBMS_SPM.LOAD_PLANS_FROM_SQLSET
New baselines are generated automatically:
•for statement that already have Baselines created (when new plans are parsed by the optimizer, as non accepted) –it is not capture!
•when creating a SQL Profile on a statement that has Baseline (as accepted)
Non accepted plans become acceptedbecause evolution or DBMS_SPM attribute change

New plan generation
SQL> alter index pp_idxinvisible;
Index altered.
N C
-------------------------------------------------------
1 20
SQL> select * from table(dbms_xplan.display_cursor);
SQL_ID 0a14b3yhux040, child number 1
-------------------------------------
select * from pp where n=:n
--------------------------------------------------------------------------
| Id | Operation| Name | Rows | Bytes | Cost (%CPU)| Time|
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT |||| 2 (100)| |
|* 1 | TABLE ACCESS FULL| PP | 1 | 6 | 2 (0)| 00:00:01 |
--------------------------------------------------------------------------

New plan generation
select sql_handle, plan_name, enabled, accepted, fixed, reproduced, sql_text
from dba_sql_plan_baselines;
SQL_HANDLEPLAN_NAMEENA ACC FIX REP SQL_TEXT
--------------------------------------------------------------------------------------------
SQL_114a395a2db6c38c SQL_PLAN_12kjtb8qvdhwc8a71e415 YES NO NOYES select * from pp where n=:n
SQL_114a395a2db6c38c SQL_PLAN_12kjtb8qvdhwcdeb317bfYES YESNO NOselect * from pp where n=:n
As the existing baseline could not be reproduced, a new plan was used, and automatically added as non accepted.
Which plan was the original?
select * from table(dbms_xplan.display_sql_plan_baseline(
plan_name=> 'SQL_PLAN_12kjtb8qvdhwcdeb317bf'));

New plan generation –11g shows wrong plan
--------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Plan name: SQL_PLAN_12kjtb8qvdhwcdeb317bfPlan id: 3736278975
--------------------------------------------------------------------------------
--------------------------------------------------------------------------
| Id | Operation| Name | Rows | Bytes | Cost (%CPU)| Time|
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT || 1 | 6 | 2 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| PP | 1 | 6 | 2 (0)| 00:00:01 |
--------------------------------------------------------------------------
---------------------------------------------------
1 -filter("N"=TO_NUMBER(:N))

New plan generation –12c shows correct plan
--------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Plan name: SQL_PLAN_12kjtb8qvdhwcdeb317bfPlan id: 3736278975
--------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------
| Id | Operation| Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT|||| 2 (100)| |
| 1 | TABLE ACCESS BY INDEX ROWID BATCHED| PP |1 |6 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN| PP_IDX |1 || 1 (0)| 00:00:01 |
------------------------------------------------------------------------------------------------------
…

No misunderstandings
Each SQL Baseline stores the original SQL execution plan?
–11g: no, it regenerates the plan using captured data
•SQLOBJ$AUXDATA
•dbms_xplan.display_sql_plan_baselinecan show a plan different from the original captured
–12c: stores the original execution plan
•SQLOBJ$PLAN

Scripts for creating new Baselines
•SQLTXPLAIN (SQLT) -MOS note 215187.1
–Tool that helps to diagnose SQL statements performing poorly
–coe_load_sql_baseline.sql–allows to add a plan generated by a modified SQL to the original
–Also useful when loading a plan from AWR (must go through SQL tuning set)

Using SQLT to binda modifiedplan
SQL_IDEXACT_MATCHING_SIGNATURE PLAN_HASH_VALUE CHILD SQL_TEXT
---------------------------------------------------------------------------------------------------
fxdv1cmv8cksa687377043604823894329329474960 select /*+ FULL(pp) */ * from pp where n =:n
0a14b3yhux0401245871306398155660452276032 0 select * from pp where n=:n
SQL> select * from dba_sql_plan_baselines;
no rows selected
SQL> stacoe_load_sql_baseline0a14b3yhux040fxdv1cmv8cksa 2932947496
…
Plans Loaded: 1
sys_sql_handle: "SQL_114a395a2db6c38c"
sys_plan_name: "SQL_PLAN_12kjtb8qvdhwc8a71e415"
SQL_IDEXACT_MATCHING_SIGNATURE PLAN_HASH_VALUE CHILD SQL_TEXT
---------------------------------------------------------------------------------------------------
fxdv1cmv8cksa687377043604823894329329474960 select /*+ FULL(pp) */ * from pp where n =:n
0a14b3yhux0401245871306398155660452276032 0 select * from pp where n=:n
0a14b3yhux040124587130639815566029329474961 select * from pp where n=:n

How SQL Plan Management interact with ...?
•Stored Outlines (desupportannounced on 11.1)
•SQL Profiles –since 10g
•Adaptive Cursor Sharing (ACS) –new 11g
•Adaptive Query Optimization (12c)
–Adaptive Plans (joins and parallel distribution methods)
–Adaptive Statistics (at compile time and at runtime))

How SQL Plan Management interact with ...?
•Stored Outlines (desupportannounced on 11.1)
•SQL Profiles –since 10g
•Adaptive Cursor Sharing (ACS) –new 11g
•Adaptive Query Optimization (12c)
–Adaptive Plans (joins and parallel distribution methods)
–Adaptive Statistics (at compile time and at runtime))
Affects plan selection/creation, but SPM is the last step!
Some bugs in the past with profiles+baselines-12980183
ACS and SPM demo: https://blogs.oracle.com/optimizer/resource/acs-spm- figures/acs-spm-script.sql

Management of new plans (evolution)
Only better performing plans are accepted considering elapsed time, logical IO and CPU time
–Plan reproducibility plays here (ACS/Binds)
11g: manually using DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE
12c: new Evolve Advisor configured as a daily autotask
–SYS_AUTO_SPM_EVOLVE_TASK
–Result report using DBMS_SPM.REPORT_AUTO_EVOLVE_TASK
–Automatically accepts new baselines performing better
•parameter ACCEPT_PLANS defaults TRUE
–Manuallytoo with DBMS_SPM.CREATE_EVOLVE_TASK
–DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE deprecated

Plan evolution in 11g
set long 100000
vare clob;
exec :e := DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(
SQL_HANDLE=>'SQL_114a395a2db6c38c',
COMMIT => 'NO');
print;

Evolve SQL Plan Baseline Report
-------------------------------------------------------------------------------
Inputs:
-------
SQL_HANDLE = SQL_114a395a2db6c38c
PLAN_NAME =
TIME_LIMIT = DBMS_SPM.AUTO_LIMIT
VERIFY = YES
COMMIT = NO
Plan: SQL_PLAN_12kjtb8qvdhwc8a71e415
------------------------------------
Plan was verified: Time used .06 seconds.
Plan failed performance criterion: 1.02 times better than baseline plan.
Baseline Plan Test Plan Stats Ratio
---------------------------------
Execution Status: COMPLETE COMPLETE
Rows Processed: 1 1
Elapsed Time(ms): .494 .101 4.89
CPU Time(ms): .444 .111 4
Buffer Gets: 2 2 1
Physical Read Requests: 0 0
Physical Write Requests: 0 0
Physical Read Bytes: 0 0
Physical Write Bytes: 0 0
Executions: 1 1
36
--------------------------------------------
Report Summary
--------------------------------------------
Number of plans verified: 1
Number of plans accepted: 0

Plan evolution in 11g
Continuing with our example:
–invisible index
set long 100000
vare clob;
COMMIT => 'NO');
print;
----------------------------------------------------------
----------------------------------------------------------
Inputs:
-------
PLAN_NAME =
VERIFY = YES
COMMIT = NO
------------------------------------
Plan was not verified.
Using cost-based plan as could not reproduce any
accepted and enabled baseline plan.
-----------------------------------------------------------
Report Summary
-----------------------------------------------------------
Number of plans verified: 0
Number of plans accepted: 0

Plan evolution in 11g –results examples
------------------------------------
Plan was verified: Time used 7,932 seconds.
Plan failed performance criterion: performance equal to baseline plan.
Plan failed performance criterion: 1,20 times worse than baseline plan.
Plan failed performance criterion: 17,5 times worse than baseline plan.
Plan verification timed out.
Error encountered during plan verification (ORA-16960).
ORA-16960: SQL Analyze no ha podidoreproducirel plan deseado.
Plan passed performance criterion.

Plan evolution on 12c
39
11g evolution deprecated but runs
set long 100000
vare clob;
COMMIT => 'NO');
print;
GENERAL INFORMATION SECTION
--------------------------------------------------------
Task Information:
-----------------------------------------
Task Name : TASK_1604
Task Owner : SYS
Execution Name : EXEC_1681
Execution Type : SPM EVOLVE
Scope : COMPREHENSIVE
Status : COMPLETED
Started : 08/09/2014 21:07:53
Finished : 08/09/2014 21:07:53
Last Updated : 08/09/2014 21:07:53
Global Time Limit : 2147483646
Per-Plan Time Limit : UNUSED
Number of Errors : 0
--------------------------------------------------------
SUMMARY SECTION
--------------------------------------------------------
Number of plans processed : 1
Number of findings : 1
Number of recommendations : 0
Number of errors : 0
--------------------------------------------------------
…

DETAILS SECTION
-------------------------------------------------------
Object ID : 2
Test Plan Name : SQL_PLAN_12kjtb8qvdhwc8a71e415
Base Plan Name : SQL_PLAN_12kjtb8qvdhwca9f022c1
SQL Handle : SQL_114a395a2db6c38c
Parsing Schema : SYS
Test Plan Creator : SYS
SQL Text : select * from pp where n=:n
Bind Variables:
-----------------------------
1 -(NUMBER): 99
Execution Statistics:
-----------------------------
Base Plan Test Plan
--------------------------------
Elapsed Time (s): .000003 .000003
CPU Time (s): 0 0
Buffer Gets: 0 0
Optimizer Cost: 2 2
Disk Reads: 0 0
Direct Writes: 0 0
Rows Processed: 0 0
Executions: 10 10
FINDINGS SECTION
--------------------------------------------------------
Findings (1):
-----------------------------
1. The plan was verified in 0.02000 seconds. It failed the benefit criterion because its verified performance was 0.66667 times worse than that of the baseline plan.
EXPLAIN PLANS SECTION
--------------------------------------------------------
Baseline Plan
-----------------------------
Plan Id : 2201
Plan Hash Value : 2851087041
---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 6 | 2 | 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID BATCHED | PP | 1 | 6 | 2 | 00:00:01 |
| * 2 | INDEX RANGE SCAN | PP_IDX | 1 | | 1 | 00:00:01 |
-----------------------------------------------------------------------------------------
------------------------------------------
* 2 -access("N"=:N)
Test Plan
-----------------------------
Plan Id : 2202
Plan Hash Value : 2322719765
---------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Time |
---------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 6 | 2 | 00:00:01 |
| * 1 | TABLE ACCESS FULL | PP | 1 | 6 | 2 | 00:00:01 |
---------------------------------------------------------------------

Plan evolution on 12c -automatic
41
SELECT owner, description, advisor_name, created, last_modified, status, recommendation_countrc
FROM dba_advisor_tasks
WHERE task_name= 'SYS_AUTO_SPM_EVOLVE_TASK';
OWNER DESCRIPTIONADVISOR_NAMECREATED LAST_MODI STATUS RC
----------------------------------------------------------------------------------
SYSAutomatic SPM Evolve Task SPM Evolve Advisor 24-MAY-13 09-AUG-14 COMPLETED 0
SELECT count(*) FROM DBA_ADVISOR_PARAMETERS
WHERE TASK_NAME = 'SYS_AUTO_SPM_EVOLVE_TASK';
COUNT(*)
----------
29
Viewing result report (same output as before):
select dbms_spm.report_auto_evolve_taskfrom dual;

Plan evolution on 12c -manually
varr varchar2(30);
vart varchar2(20);
exec :t := 'EVOTASK';
--with no parameter will consider all non ACCEPTED baselines
exec :r := dbms_spm.create_evolve_task(task_name=>:t, description=>:t,
plan_name=>'SQL_PLAN_12kjtb8qvdhwc8a71e415');
exec :r := dbms_spm.execute_evolve_task(:t, 'run1', 'first evolve run');
SELECT advisor_name, created, last_modified, status, how_created, recommendation_countrc
FROM dba_advisor_tasks
WHERE task_name= :t;
ADVISOR_NAMECREATED LAST_MODI STATUS HOW_CREATEDRC
-------------------------------------------------------------------------------------
SPM Evolve Advisor 09-AUG-14 09-AUG-14COMPLETED CMD0
vare clob;
exec :e := dbms_spm.report_evolve_task(:t);
col e for 150
print eSame report as before

Plan evolution on 12c -manually
Recommendation section: provides command to execute
Findings (1):
-----------------------------
1. None of the accepted plans were reproducible.
Recommendation:
-----------------------------
Consider accepting the plan. Execute
dbms_spm.accept_sql_plan_baseline(task_name=> 'EVOTASK', object_id=> 2, task_owner=> 'SYS');

Implementing automatic evolution on 11g
44
declare
cursor c_nuevos_baselinesis
select sql_handle, PLAN_NAME, (select count(1) from DBA_SQL_PLAN_BASELINES b2
where b.sql_handle=b2.sql_handle and b2.accepted='YES') aceptados
from DBA_SQL_PLAN_BASELINES b
where enabled='YES' and accepted='NO' and created > trunc(sysdate)-7
order by sql_handle, PLAN_NAME, created;
begin
dbms_output.put_line('varr long;');
dbms_output.put_line('set long 100000');
dbms_output.put_line('spool evolve-results-'||to_char(sysdate,'yyyymmdd')||'.txt');
for r_blin c_nuevos_baselinesloop
dbms_output.put_line('##################');
if r_bl.aceptados> 0 then
dbms_output.put_line('exec :r:=dbms_spm.evolve_sql_plan_baseline(sql_handle=> '''||r_bl.sql_handle||
''', plan_name=>'''||r_bl.plan_name||''', commit => ''NO'');');
dbms_output.put_line('print;');
end if;
dbms_output.put_line('select * from table(dbms_xplan.display_sql_plan_baseline('||
'sql_handle=>'''||r_bl.sql_handle||''', plan_name=>'''||r_bl.plan_name||'''));');
end loop;
dbms_output.put_line('spool off');
end;
/

Implementing automatic evolution on 11g
45
Sample run:
set serverouputon
spool toevolve.sql
@autoevo11g
spool off
@toevolve
--to evolve.sqlgenerated:
varr long;
set long 100000
spool evolve-results-20140810.txt
##################
exec :r:=dbms_spm.evolve_sql_plan_baseline(sql_handle=> 'SQL_114a395a2db6c38c', plan_name=>'SQL_PLAN_12kjtb8qvdhwcdeb317bf', commit => 'NO');
print;
select * from table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SQL_114a395a2db6c38c', plan_name=>'SQL_PLAN_12kjtb8qvdhwcdeb317bf'));
spool off
Usually the result is a long report. This case is the same as seen today

Challenges?
•SQL without using bind variables
-Different statements (signature/sql_id), different baselines
-Change app code. Last resource CURSOR_SHARING=FORCE
•SQL with too many bind variables
-Maybe cannot reproduce plan –needs a trace to confirm
-Maybe errors when evolving new ones –(Bug 19326647 on 11.2.0.3)
•SQL already using hints
-Test original with alter session set _optimizer_ignore_hints
•SQL already using SQL Profiles
-Test original with alter session set sqltune_category=‘NNN';

Challenges
Why my SQL has baselines and none is being used?
1)SPM disabled by parameter
2)Stored outline created –use it and ignore baselines
3)Similar objects on different schemas
4)Baseline cannot be reproduced
5)Bugs

Challenge -similar objects on different schemas
Common on database consolidation scenarios
•Baselines are global for the database (not per schema)
•Same table names, different schemas, same SQL
–Look at object definition/indexes on each schema
Column PARSING_SCHEMA_NAME in DBA_SQL_PLAN_BASELINEShelps
–CREATOR and ORIGIN can lead too

Challenge -baseline cannot be reproduced
•Object changes: if tables used by SQL baseline changes, it can stop being used
–Remember 11g does not stores captured plans when investigating
•Same PLAN_HASH_VALUE2?
–minor bugs played here
•Trace to the rescue:
–It can be reproduced? => session level
•10053 / spm_tracing/ SQL_Plan_Management
–Statement level to capture global activity --new connections only
•alter system set events 'trace[rdbms.SQL_Optimizer.*][sql: 0a14b3yhux040]’
–If using connection pools
•dbms_sqldiag.dump_trace(…p_component=>'Compiler‘)

Troubleshooting SPM –trace alternatives
Global statement trace for already existing and new connections:
dbms_sqldiag.dump_trace(p_sql_id=>'0a14b3yhux040', p_child_number=>0,
p_component=>'Compiler', p_file_id=>'trace_0a14b3yhux040');
SPM Trace at session level:
ALTER SESSION SET EVENTS'trace[RDBMS.SQL_Plan_Management.*]';
Internal SPM trace generation (more detailed):
EXEC dbms_spm.configure('spm_tracing',1);
--validate current settings:
SELECT * FROM sys.smb$configWHERE parameter_name='SPM_TRACING';
Classic optimizer trace, which includes SPM standard trace:
ALTER SESSION SET EVENTS 'trace[sql_optimizer.*]';
--same but for in older Oracle versions
ALTER SESSION SET EVENTS='10053 trace name context forever, level 1';

Troubleshooting SPM –trace results
When a Plan Baselineis found and used:
SPM: statement found in SMB
SPM: cost-based plan found in the plan baseline, planId= 3736278975
SPM: cost-based plan successfully matched, planId= 3736278975
When no matching Plan Baseline found, adding new one as non-accepted:
SPM: statement found in SMB
SPM: setup to add new plan to existing plan baseline, sig = 1245871306398155660, planId= 2322719765
SPM: planId'sof plan baseline are: 3736278975
SPM: using qksanto reproduce, cost and select accepted plan, sig = 1245871306398155660
SPM: failed to reproduce the planusing the following info:
SPM: generated non-matching plan:
SPM: couldn't reproduce any enabled+acceptedplan so using the cost-based plan, planId= 2322719765
SPM: add new plan: sig = 1245871306398155660, planId= 2322719765
SPM: new plan added to existing plan baseline, sig = 1245871306398155660, planId= 2322719765
SPM: REPRODUCED status changed to NO: sig = 1245871306398155660, planName= SQL_PLAN_12kjtb8qvdhwcdeb317bf

Usage decision
•optimizer_capture_sql_plan_baselines= TRUE
OR
•created when needed by each SQL?
No silver bullet, choose the better one for your environment
Use case:
•some queries from a specific program would benefit from parameter=value
–instead of changing the parameter and avoid this functionality to be used on other cases which would be beneficial, SQL baselines are created just for those programs
–It is more manual work to have a functionality available for the other users

Daily management overhead
Evaluate autotasksrecommendations:
•Trusting automatic creation of SQL Profiles/Baselines?
•SQL Tuning Advisor (SQLTA) / SPM Evolve Advisor (12c)
•Several views and reports to explore their results using SQL
–dba_advisor_tasks/ dba_advisor_rationale
•IF SQLTA recommends a SQL profile for a SQL that has no baselines
–create the new SQL profile
–move it to a SQL baseline
–Disable SQL profile
•On 11g: evaluate daily new baselines evolving them
–How to deal with heavy activity and lots of new plans? AWR helps

Daily management example approach
54
•Better performing evolved plans should be testing with a variety of binds on test environment before accepting them
•Disable evaluated and confirmed non good plans
exec :r :=DBMS_SPM.ALTER_SQL_PLAN_BASELINE (sql_handle=> 'SQL_114a395a2db6c38c', plan_name=>'SQL_PLAN_12kjtb8qvdhwca9f022c1',
attribute_name=>'enabled', attribute_value=>'NO');
select count(*), count(distinct sql_handle) sqls, accepted, enabled
from dba_sql_plan_baselines
group by accepted, enabled;
COUNT(*) SQLS ACC ENA
---------------------
13792 13788 YES YESare in use by optimizer
20 16 YES NO
5588 3063 NO YES
210 25 NO NO

55
---------------------
20 16 YES NO used but manually disabled because of problems found
5588 3063 NO YES
210 25 NO NO

56
---------------------
5588 3063 NO YESnew plans that needs evaluation
210 25 NO NO

57
---------------------
210 25 NO NOalready evaluated new plans nod performing good

58
---------------------
210 25 NO NOalready evaluated new plans nod performing good
Will you read a report with 5588 evolutions? Need an improved approach

Choosing what to evolve on 11g using stats
59
Which statements are now running in more than 5s and have non accepted baselines?
select * from (
select s.inst_id, s.sql_id
,min(s.first_load_time) min_load_time
,sum(s.executions) eje
,round(sum(s.elapsed_time)/1000000/greatest(sum(s.executions),1),2) avg_sec
,round(sum(s.disk_reads)/greatest(sum(s.executions),1),2) avg_reads
,round(sum(s.buffer_gets)/greatest(sum(s.executions),1),2) avg_gets
,dense_rank() over (order by sum(s.elapsed_time)/greatest(sum(s.executions),1) desc) rank
from gv$sqls, DBA_SQL_PLAN_BASELINES b
where s.FORCE_MATCHING_SIGNATURE=b.signature
and b.enabled='YES' and b.accepted='YES'
and exists (select 1 from DBA_SQL_PLAN_BASELINES b2
where b.sql_handle=b2.sql_handle and b2.enabled='YES' and b2.accepted='NO')
group by s.inst_id, s.sql_id
having sum(s.elapsed_time)/greatest(sum(s.executions),1)/1000000 > 5)
where rank < 50
order by rank desc;

Choosing what to evolve on 11g using stats
60
Output example:
INST_ID SQL_ID MIN_LOAD_TIME EJE AVG_SEC AVG_READS AVG_GETS RANK
--------------------------------------------------------------------------------------------
1 4baj8ju7nqpvt 2014-06-22/24:30:20 2 4,34 4872 23787 15
2 7n8hbzpruj4nu 2014-06-22/07:03:04 327 4,42 2007,47 74787,87 14
2 t0jxh8b7b4at2 2014-20-22/04:02:48 2 4,44 223 2427 13
3 7n8hbzpruj4nu 2014-06-22/07:47:28 569 7,28 2342,87 78480,22 12
1 t22bnbazvj87x 2014-06-22/20:03:42 38 8,23 2348,8 3444,2 11
3 t2qx4bv4y383b 2014-06-22/23:38:32 28 8,38 4207,32 47883,72 10
2 arpa78rrkhp80 2014-06-22/08:27:28 240 8,42 2242,8 4747,24 9
2 t7qntjn4aaj8k 2014-06-22/22:48:27 22 8,47 2787,33 4780,83 8
2 04h4pq4tpn238 2014-06-22/08:32:08 32 8,78 2207,83 20427,44 7
3 bqtx4q2jas08u 2014-06-22/02:43:22 34 20,33 2737,28 3444,2 6
3 t2qx4bv4y383b 2014-06-22/22:24:02 22 20,88 4780,4 47282,78 5
2 7qbkbt7h00wtw 2014-06-22/07:30:37 404 23,42 2228,87 73488,07 4
2 0s2b777vta78b 2014-06-22/07:28:02 283 24,8 2377,83 273342,87 3
1 7qbkbt7h00wtw 2014-06-08/04:04:27 647 27,43 2788,34 80848,38 2
2 2rnttntn3xb4r 2014-06-22/23:48:28 22 32,77 7273,77 42244,87 1
15 rows selected.
Needs another join to show baseline plan_name. That idea next with AWR

Choosing what to evolve on 11g using AWR
61
Non accepted baselines of statements with executions times max/min variations of 5 times
•AWR has historical data, needs Diagnostic Pack license
Output example:
SQL_HANDLE SQL_ID MAXE MINE PLANS #accept PLAN_NAME CREATED ACC FIX
--------------------------------------------------------------------------------------------------------------
SQL_x1c4f31970638583 y283zg7xww7am 4,23 ,31 7 1 SQL_PLAN_s7554kd1hzk11258e3b6f 08/07/14 14:41:23 NO NO
4,23 ,31 7 1 SQL_PLAN_s7554kd1hzk116e35c426 06/07/14 11:48:34 NO NO
4,23 ,31 7 1 SQL_PLAN_s7554kd1hzk118d733646 21/07/14 14:06:03 NO NO
4,23 ,31 7 1 SQL_PLAN_s7554kd1hzk11900895ab 21/07/14 17:04:24 NO NO
SQL_d8ee9cd8489c1506 d70w2c9n04bky 11,02 ,7 5 2 SQL_PLAN_djvnwv149s50p0de525df 17/06/14 17:50:45 NO NO
SQL_50563b1a5e7c3515 cdxqhv810sguq 142,12 4,51 12 4 SQL_PLAN_62t9v39g7sdj6e14b0faa 17/06/14 09:37:12 NO NO
SQL_a69a285b67c3ab33 7jr0hhnrg5qpd 5,12 ,54 4 0 SQL_PLAN_5sw7au49da15rb55d4723 18/06/14 14:09:54 NO NO
5,12 ,54 4 0 SQL_PLAN_5sw7au49da15r1224e506 06/06/14 13:21:12 NO NO
5,12 ,54 4 0 SQL_PLAN_5sw7au49da15r92eca281 12/06/14 11:50:16 NO NO

Choosing what to evolve on 11g using AWR
62
with sqlhas (
select FORCE_MATCHING_SIGNATURE, sql_id, count(1) plans, max(elap_xeje) maxe, min(elap_xeje) mine
from (select h.FORCE_MATCHING_SIGNATURE, sql_id, plan_hash_valueplan_hv
,round(sum(h.elapsed_time_delta)/sum(h.executions_delta)/1000000,2) elap_xeje
from DBA_HIST_SQLSTAT h
where snap_id>=(select min(snap_id) from dba_hist_snapshotwhere begin_interval_time>=trunc(sysdate)-30)
and dbid=(select dbidfrom v$database) and instance_numberin (1,2,3)
and h.executions_delta> 0
and h.FORCE_MATCHING_SIGNATUREin (
select b.signaturefrom DBA_SQL_PLAN_BASELINES b
where b.enabled='YES' and b.accepted='NO')
group by FORCE_MATCHING_SIGNATURE, sql_id, plan_hash_value)
group by FORCE_MATCHING_SIGNATURE, sql_id
having max(elap_xeje)/(case min(elap_xeje) when 0 then 1 else min(elap_xeje) end) > 5)
select sql_handle, signature, sqlh.sql_id, sqlh.maxe, sqlh.mine, sqlh.plans,
(select count(1) from DBA_SQL_PLAN_BASELINES b2
where b.sql_handle=b2.sql_handle and b2.accepted='YES' and b2.enabled='YES') "#accept"
,PLAN_NAME, created, accepted, fixed
from DBA_SQL_PLAN_BASELINES b, sqlh
where b.enabled='YES' and b.accepted='NO' and b.created> trunc(sysdate)-30
and b.signature= sqlh.FORCE_MATCHING_SIGNATURE
order by sql_handle, sql_id, maxe;

Example of bug found –11.2.0.2
SQL_ID c2408ff99yj8u, child number 0
-------------------------------------
SELECT DATA, COUNT(*) FROM BIG_TABLE WHERE (((((((((DATA LIKE :1 ) OR (DATA LIKE :2 )) OR
(DATA LIKE :3 )) OR (DATA LIKE :4 )) OR (DATA LIKE :5 )) OR (DATA LIKE :6 )) OR (DATA LIKE :7 )) OR
(DATA LIKE :8 )) AND (STATE IN (:9 , :10 , :11 , :12 , :13 , :14 , :15 , :16 , :17 , :18 , :19 , :20 , :21 , :22 , :23 , :24 , :25 , :26 , :27 , :28 , :29 , :30 , :31 , :32 ))) GROUP BY DATA
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 7504 (100)| |
| 1 | HASH GROUP BY | | 16 | 1536 | | |
| 2 | CONCATENATION | | | | | |
|* 3 | INDEX RANGE SCAN| BIG_TABLE_CIDN | 1668 | 156K| 938 (1)| 00:00:12 |
..
|* 10 | INDEX RANGE SCAN| BIG_TABLE_CIDN | 1165 | 109K| 938 (1)| 00:00:12 |
----------------------------------------------------------------------------------------------
...
Note
-SQL plan baseline SQL_PLAN_8vdc1f1da6d7sa0mtur14used for this statement

--Plan baselines for this statement:
col created for a25
select PLAN_NAME, ENABLED, accepted, fixed, created, executions, optimizer_cost
from DBA_SQL_PLAN_BASELINES
where sql_handle='SQL_114a395a2db6c38c' and enabled='YES'
order by created;
PLAN_NAME ENA ACC FIX CREATED EXECUTIONS OPTIMIZER_COST
----------------------------------------------------------------------------------------
SQL_PLAN_8vdc1f1da6d7sa0mtur14YES YESNO 05/08/14 16:11:26,000000 1 7504
SQL_PLAN_0sa1muctuur8ve7e49070 YES NO NO05/08/14 17:29:45,000000 0 2039
2 rows selected.
--Want to evaluate the new plan found, not accepted yet

--evolving the new plan:
varr clob;
set long 10000
exec :r := dbms_spm.evolve_sql_plan_baseline(sql_handle=> 'SQL_114a395a2db6c38c',
plan_name=>'SQL_PLAN_0sa1muctuur8ve7e49070', commit => 'NO');
print;
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Inputs:
-------
PLAN_NAME = SQL_PLAN_0sa1muctuur8ve7e49070
VERIFY = YES
COMMIT = NO
Plan: SQL_PLAN_0sa1muctuur8ve7e49070
------------------------------------
Plan was verified: Time used ,507 seconds.
Error encountered during plan verification (ORA-1008).
ORA-01008: no todaslasvariables hansidoenlazadas
Bug 14007103 discarded
Bug 19326647 opened

Summary review
•SPM enabled by default, but not capture
•No extra license, available only on Enterprise edition
•Baseline need to be acceptedAND enabled to be used
•SQL needs to run more than once to be considered
•Baselines are global -not per schema
•Evolve advisor (autotask) in 12c, manual evolution in 11g.
•Don’t trust evolution results, test it!
•SQL Trace when in doubt (statement level!)
•Needs a good understanding to troubleshoot

Questions?
67
calero@pythian.com
@ncalerouy
http://www.linkedin.com/in/ncalero

References
•SPM in Oracle 11g (Nov 2010): http://www.oracle.com/technetwork/database/bi- datawarehousing/twp-sql-plan-management-11gr2-133099.pdf
•SPM in Oracle 12c (Jun 2013): http://www.oracle.com/technetwork/database/bi- datawarehousing/twp-sql-plan-mgmt-12c-1963237.pdf
•Oracle 12c Tuning Guide -Managing SQL Plan Baselines: http://docs.oracle.com/database/121/TGSQL/tgsql_spm.htm#TGSQL94621
•Oracle 12c Tuning Guide -Query Optimizer: http://docs.oracle.com/database/121/TGSQL/tgsql_optcncpt.htm#TGSQL192
•Oracle 11c Tuning Guide -Query Optimizer: http://docs.oracle.com/cd/B28359_01/server.111/b28274/optimops.htm
•Oracle Optimizer development team Blog: https://blogs.oracle.com/optimizer

My Experience Using Oracle SQL Plan Baselines 11g/12c

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