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1 Oracle OpenWorld 2009 Tim Quinlan TLQ Consulting Inc. Guaranteeing High Performing SQL through Plan Stability and Management.

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Presentation on theme: "1 Oracle OpenWorld 2009 Tim Quinlan TLQ Consulting Inc. Guaranteeing High Performing SQL through Plan Stability and Management."— Presentation transcript:

1 1 Oracle OpenWorld 2009 Tim Quinlan TLQ Consulting Inc. Guaranteeing High Performing SQL through Plan Stability and Management

2 2 Oracle OpenWorld 2009 Plan Stability Part 1: Taking advantage of Plan Stability. –What is Plan Stability and why do we need it? –Getting started, turning it on and capturing outlines. –Making an outline active and keeping it active –Monitoring: is an outline being used? –Managing outlines: scripts, issues, schema maintenance –Moving outlines Part 2: SQL Plan Management, the next generation –SQL Baselines vs. Stored Outlines –Baselines: fixed and non-fixed; capturing; moving –SQL Management Base (SMB) –Maintenance: packages, views, export, import –Managing Baselines: purging; config. parms; displaying; migrating to SQL Plan Baselines.

3 3 Oracle OpenWorld 2009 Part 1: Taking advantage of Plan Stability Overview of Part 1 –What is Plan Stability and why do we need it? –Getting started, turning it on and capturing outlines. –Categories and how we use them –Making an outline active and keeping it active –Monitoring: is an outline being used? –Managing outlines: scripts, issues, schema maintenance –Moving outlines

4 4 Oracle OpenWorld 2009 Part 1: Plan Stability What is Plan Stability and why do we need it? Have you ever had an SQL statement suddenly run much longer for no reason? Why do access paths change? –Change in data volumes and statistics –Change in objects: example index changes –Optimizer settings: e.g. memory settings –Oracle version or patch –Deployment of new or changed modules and recompiles –Change to the environment e.g. server memory settings or usage.

5 5 Oracle OpenWorld 2009 What is an outline? –Method of saving a named execution plan for one SQL statement. This is done by storing hints to influence the access path. The hints are saved rather than the actual execution plan. –Future SQL, exactly matching the original SQL, can use the stored hints to affect the access path. Part 1: Plan Stability What is Plan Stability and why do we need it?

6 6 Oracle OpenWorld 2009 Caution: the performance of the stored execution plan may degrade over time. –Based on statistics and an environment that may no longer be valid. –Contradicts the purpose of the optimizer. –Requires management and should only be used where necessary and as a temporary fix. Go back to the original SQL, application design and or object (e.g. index) design. Part 1: Plan Stability What is Plan Stability and why do we need it?

7 7 Oracle OpenWorld 2009 Part 1: Plan Stability What is Plan Stability and why do we need it? How does SQL match an outline? One-to-one correlation between an SQL statement & an outline. Similar statements can share an outline using literals rather than bind variables. –When created with create_stored_outline procedure not with create_outline statement. –When the statement is captured AND executed using cursor_sharing set to similar. –If you embed new hints into SQL, that new SQL will no longer match the stored outline. –Outline SQL text and category name are both used to see if a plan is in cache. Ensures that the proper category is used.

8 8 Oracle OpenWorld 2009 Part 1: Plan Stability What is Plan Stability and why do we need it? Is the access path guaranteed? –No. Hints are stored, but the hints do not cover every possible access path permutation and combination. –So, the hints are taken together with the database statistics and run-time environment to develop the access path. Home-built and 3 rd party applications –Can both benefit from stored outlines.

9 9 Oracle OpenWorld 2009 Part 1: Plan Stability What is Plan Stability and why do we need it? The outln schema –The schema where stored outlines are saved in the database. –OL$, OL$HINTS, OL$NODES tables –These tables cannot be changed directly with insert, update, delete statements. –SYS schema views user_outlines, user_outline_hints, ku$_outline_view views.

10 10 Oracle OpenWorld 2009 Part 1: Plan Stability Using Categories to Manage Outlines What are Categories and how are they used? –Simplify plan management –Create Outline statement and/or the create_stored_outlines init parm allow you to specify a category. Otherwise, goes to category DEFAULT. All stored outlines go to that category until the category name is reset.

11 11 Oracle OpenWorld 2009 Part 1: Plan Stability Using Categories to Manage Outlines What are Categories and how are they used? (cont.) –A category can be enabled so outlines can be used by SQL. –An outline can be created & stored in a category, without being used This allows you to keep versions or a history of outlines. –After an outline has been captured, it can remain in this category or can be moved to another category. The new category could be active allowing this outline to be a candidate for future SQL.

12 12 Oracle OpenWorld 2009 Part 1: Plan Stability Using Categories to Manage Outlines Changing categories with alter outline –You can capture a plan in one category and then move it to another to make it active. SQL> select name, owner, category from dba_outlines where category='Client_CashTxns'; NAME OWNER CATEGORY SYS_OUTLINE_ APPOWNER CapturedCat SQL> alter outline SYS_OUTLINE_ change category to UsePlan; NAME OWNER CATEGORY SYS_OUTLINE_ APPOWNER UsePlan –Use Alter Outline to enable an individual statement; rename an outline; move an outline to another Category.

13 13 Oracle OpenWorld 2009 Private outlines. –A private outline is only seen in the current session with data residing on the parsing schema. –For a private outline to be used by other sessions, they must be explicitly saved to a public area. –Retrieved from session private area with use_private_outlines as opposed to the public area with use_stored_outlines. –Set parm use_private_outlines to enable this. This and use_stored_outlines are system or session specific and not initialization parms. Part 1: Plan Stability Using Categories to Manage Outlines (cont.)

14 14 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines When do we capture outlines? –Regular, scheduled capture (example monthly) –Before upgrades A valuable backup plan in case a single access path causes problems. –Capturing outlines in test Perform volume or stress testing and capture the outlines. These can be moved to Prod just in case theyre needed. –Moving from RBO to Cost-Based Before the move, capture the outlines from the rule-based optimized. After the switch, you will have the outlines in case they are needed.

15 15 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Parameters –parms that need to be consistent across execution environments for outlines to function as expected: optimizer_features_enable, query_rewrite_enable and star_transformation_enable –parm create_stored_outlines set to true will create outlines automatically. Set to false to turn this off. Use dbms_outln.drop_unused proc to remove outlines where SQL uses literals and will likely not be used. Privileges –create any outline privilege needed on schema to create outlines. Needed to run the create outline statement.

16 16 Oracle OpenWorld 2009 Creating Outlines –Can be granular > for 1 specific SQL statement - OR - > for all SQL statements over a period of time. Part 1: Plan Stability Getting started, turning on and capturing outlines

17 17 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Creating Outlines for all SQL in a Schema We capture stored outlines once every month for 2 hours for a specific application schema E.g. Capture outlines in a single category named MONTHLY2009SEP10: GRANT CREATE ANY OUTLINE TO SCHEMANAME; variable v_sodate varchar2(15); begin select to_char(sysdate,'YYYYMONDD-DY') into :v_sodate from dual; :v_sql := 'alter system set create_stored_outlines = MONTHLY' || :v_category ; execute immediate :v_sql; end;

18 18 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines How can I see if the Stored Outlines are being created? SQL> select value from v$parameter where name = 'create_stored_outlines'; VALUE MONTHLY2008DEC10 SQL> select owner, category, count(*) from dba_outlines group by owner, category; OWNERCATEGORY COUNT(*) SCOTTMONTHLY2008DEC … let some time go by and run this again … SQL> select owner, category, count(*) from dba_outlines group by owner, category; OWNERCATEGORY COUNT(*) SCOTTMONTHLY2008DEC10 478

19 19 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Turn off the capture –Check that the stored outline is being captured SQL> select value from v$parameter where name = 'create_stored_outlines'; VALUE MONTHLY2008DEC10 SQL> select owner, category, count(*) from dba_outlines group by owner, category; CATEGORY COUNT(*) MONTHLY2008DEC –Turn off the capture SQL> alter system set create_stored_outlines = false; –Check that this is turned off: SQL> select value from v$parameter where name = 'create_stored_outlines'; VALUE FALSE

20 20 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines There are other ways to capture outlines. Capturing Outlines for specific SQL in cache –Find the SQL using the sql_text as input: SQL> select sql_id, hash_value, child_number, sql_text from v$sql where upper(sql_text) like upper('MERGE INTO detailtable%'); SQL_ID HASH_VALUE CHILD_NUMBER SQL_TEXT 36k6xhn2zmv3q MERGE INTO detailtable… –Make sure the user has authority to create outlines: SQL> GRANT CREATE ANY OUTLINE TO appluser;

21 21 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Capturing Outlines for specific SQL in cache (cont.) Create a stored outline for an SQL cursor currently in the Shared Pool. You need the HASH_VALUE and CHILD_NUMBER from V$SQL for the SQL you want to add to a stored outline category. –From the previous slide Use hash_value as first parm. Put this outline into its own category named OneOutlnCat: exec dbms_outln.create_outline( , 0,OneOutlnCat');

22 22 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Look at the execution plan using DBMSXPLAN and the SQL_ID SELECT * FROM table(DBMS_XPLAN.DISPLAY_CURSOR('36k6xhn2zmv3q',0)); DBMSXPLAN gives you: –SQL_ID –Hash_Value –Execution plan of the SQL that executed.

23 23 Oracle OpenWorld 2009 Part 1: Plan Stability Getting started, turning on and capturing outlines Capture Outlines for specific SQL in cache (cont.) Export the single outline exp '"/ AS SYSDBA"' log=${DMP_DIR}/expOneOutln.log buffer= file=${DMP_DIR}/expOneOutln.dmp tables='outln.ol$','outln.ol$hints' query=\"where category=\OneOutlnCat\'\" Import the Outline to a new database imp '"/ AS SYSDBA"' log=${DMP_DIR}/impOneOutln.log fromuser=OUTLN touser=OUTLN buffer= commit=y ignore=y file=${DMP_DIR}/expOneOutln.dmp grants=n indexes=n rows=y constraints=n

24 24 Oracle OpenWorld 2009 Part 1: Plan Stability Using a Stored Outline in your Application Keeping an Outline Active Can an outline become inactive after its been turned on? –Yes – for example, if the database is shutdown and started. –You may want to have a startup script or trigger to ensure these are enabled. Making outlines active by category or for specific SQL –Making a category active. SQL> alter system set use_stored_outlines=UseThisCategory; - Use_stored_outlines: set to a specific category; set to TRUE for default category; set to FALSE to turn off.

25 25 Oracle OpenWorld 2009 Part 1: Plan Stability Monitoring: is an outline being used? Check the outline_category column in v$sql outline_sid column is 0 for a public outline or has the session sid for a private outline. SQL> Select outline_category, first_load_time, last_load_time, last_active_time, sql_text From v$sql Where outline_category is not null; OUTLINE_CATEGORYSQL_TEXT FIRST_LOAD_TIME LAST_LOAD_TIME LAST_ACTIVE_TIME UseThisCategorySelect ….. From …. Where … /09:22: /07:56:13 29-JAN-09 12:35:41

26 26 Oracle OpenWorld 2009 Part 1: Plan Stability Managing Outlines –Managing outlines: scripts, issues, schema maintenance –Use packages DBMS_OUTLN and DBMS_OUTLN_EDIT to manage outlines & categories. execute_catalog_role needed on dbms_outln. public can execute dbms_outln_edit. –Manipulating a stored outline Outlines can be edited manually using dbms_outln_edit. Can be edited with the outline editor in enterprise manager.

27 27 Oracle OpenWorld 2009 Part 1: Plan Stability Managing Outlines- edit Outline steps 1.Make sure the schema where the outline is to be edited has the create any outline privilege. 2.Connect to the schema where the outline is to be edited. 3.Clone the outline to a private one. create private outline new_outln from old_outln; 4.Use the enterprise manager outline editor or dbms_outln_edit to edit the outline. -For example, to change hints.

28 28 Oracle OpenWorld 2009 Part 1: Plan Stability Managing Outlines- edit Outline steps (cont.) 5When using dbms_outln_edit –Use change_join_pos if you want to change the join position –Resync the stored outline definition using one of: exec dbms_outln_edit.refresh_private_outline (newname); create private outline new_outln from private new_outln; –You can also refresh with alter system flush shared pool 6Test the new outline with the edits –Set use_private_outlines=true and run explain plan or run the SQL statement. 7Once youre happy with the edits, publish the new outline: –create or replace outline old_outln from private new_outln; 8Disable private outline use: –Use_private_outlines=false;

29 29 Oracle OpenWorld 2009 Managing Outlines: scripts, issues, schema Maintenance –Managing outlines: views schema maintenance and purging/removing outlines looking at hints startup issues –Moving Outln objects to another tablespace or database. –Capturing outlines on a regular basis

30 30 Oracle OpenWorld 2009 Managing Outlines: scripts, issues, schema Maintenance Outline Views to query [all|dba|user]_outlines [all|dba|user]_outline_hints Get name, text and to see if an outline is enabled for a category Select name, sql_text, enabled From user_outlines where category = CAT1; To see the hints used by an outline: Select hint from user_outline_hints where name = OUTLN_NAME_1;

31 31 Oracle OpenWorld 2009 Managing Outlines: scripts, issues, schema Maintenance To see the hints – example of an index being used: SQL> select sql_text from dba_outlines where name = 'SYS_OUTLINE_ select specialtaxrate from planaccount where accountid = :B1 SQL> Select node, stage, join_pos, hint from dba_outline_hints Where name = 'SYS_OUTLINE_ order by 1,2,3; NODE STAGE JOIN_POS SQL_TEXT ALL_ROWS OPT_PARAM('optimizer_index_caching' 90) OPTIMIZER_FEATURES_ENABLE(' ') IGNORE_OPTIM_EMBEDDED_HINTS OPT_PARAM('optimizer_index_cost_adj' 10) (planaccount".accountid"))

32 32 Oracle OpenWorld 2009 Managing Outlines: scripts, issues, schema Maintenance Removing outlines: automate purging of old outline categories that are more than approximately 6 months old. spool StoredOutlineMonthlyDropOldCategories.sql SELECT 'spool StoredOutlnMthlyCatDropOld.lst' from dual; SELECT 'set echo on heading on feedback on verify on' from dual; SELECT 'select category, count(*) from dba_outlines', 'where owner = ''RPMOWN'' and category like ''MONTHLY%''', 'group by category;' from dual; SELECT distinct 'exec dbms_outln.drop_by_cat(''' || category || ''');' from dba_outlines where owner = 'RPMOWN' and category like 'MONTHLY%' and timestamp < sysdate - 180; SELECT 'spool off' from dual; spool off

33 33 Oracle OpenWorld 2009 Moving outline tables from the System tablespace 1. Run checks before the move to ensure Outlines are working 2. Export outln exp '"/ AS SYSDBA"' log=${MOVETS_DIR}/expOutlnMoveTS.log owner=outln buffer= file=${MOVETS_DIR}/expOutlnMoveTS.dmp grants=y indexes=y rows=y constraints=y consistent=y triggers=y direct=n 3. Make security changes in SQL*Plus and drop the tables. SQL> revoke unlimited tablespace from outln; SQL> alter user outln default tablespace sysaux; SQL> alter user outln quota unlimited on sysaux; SQL> drop table outln.ol$; SQL> drop table outln.ol$HINTS; SQL> drop table outln.ol$NODES; Part 1: Plan Stability Moving Outlines

34 34 Oracle OpenWorld 2009 Moving outlines from the System tablespace (cont.) 4. Run the import imp '"/ AS SYSDBA"' log=${MOVETS_DIR}/impOutlnMoveTS.log fromuser=OUTLN touser=OUTLN buffer= commit=y ignore=y file=${MOVETS_DIR}/expOutlnMoveTS.dmp grants=y indexes=y rows=y constraints=y 5. Compile invalid views under SYS. 6. Run checking after the move to ensure all objects are valid. Part 1: Plan Stability Moving Outlines

35 35 Oracle OpenWorld 2009 Moving outlines to another Database Outlines of individual SQL statements and categories can be moved from one database to another. –Use Categories to help accomplish this Steps are as follows: 1) Get the SQL select sql_id, hash_value, child_number, sql_text from v$sql where sql_text like 'INSERT%INTO tmpSTM_CashTxns%'; SQL_ID HASH_VALUE CHILD_NUMBER SQL_TEXT jwfufu5zbjp INSERT /*+ APPEND */ INTO …. Part 1: Plan Stability Moving Outlines

36 36 Oracle OpenWorld 2009 Moving outlines to another Database (cont.) 2) Get the Plan using the SQL_ID select * from table(DBMS_XPLAN.DISPLAY_CURSOR('7jwfufu5zbjp1',0)); 3) Create an outline in its own new category using the hash value exec dbms_outln.create_outline( , 0,New_Category'); 4) See if the category exists select name, owner, category from dba_outlines where category=New_Category'; NAME OWNER CATEGORY SYS_OUTLINE_ OWNER1 New_Category 5) Change the category, if you wish alter outline SYS_OUTLINE_ change category to MOVEPLAN; Part 1: Plan Stability Moving Outlines

37 37 Oracle OpenWorld 2009 Moving outlines to another Database (cont.) 6) Export the Outline exp '"/ AS SYSDBA"' log=${MOVETS_DIR}/expOutln.log buffer= file=${MOVETS_DIR}/expOutln.dmp tables='outln.ol$','outln.ol$hints' query=\"where category=\MOVEPLAN\'\" 7) Import the Outline to the new database imp '"/ AS SYSDBA"' log=${MOVETS_DIR}/impOutln.log fromuser=OUTLN touser=OUTLN buffer= commit=y ignore=y file=${MOVETS_DIR}/expOutln.dmp grants=n indexes=n rows=y constraints=n Part 1: Plan Stability Moving Outlines

38 38 Oracle OpenWorld 2009 Part 1: Plan Stability Wrap-up of Part 1 –Use categories to manage outlines –Using the steps shown will start you on your way to managing access paths. Provides an excellent fallback plan if performance degrades.

39 39 Oracle OpenWorld 2009 Part 2: SQL Plan Management, The Next Generation: Topics Covered –SQL Baselines vs. Stored Outlines –Baselines: fixed and non-fixed; capturing automatically and manually; moving baselines. –Accepting plans to add to a baseline. Getting plans from SQL Tuning Sets, AWR snapshots & cursor cache. –SQL Management Base (SMB) –Maintenance packages, views, export, import –Managing Baselines SMB space management, purging; config. parms; displaying baselines; migrating from Stored Outlines to SQL Plan Baselines.

40 40 Oracle OpenWorld 2009 SQL Baselines vs. Stored Outlines –What is an SQL Baseline? –SQL Baselines vs. Stored Outlines SQL Baselines are used for the same reasons that we used Outlines. SQL Baselines can evolve over time to improve performance. –They are used to prevent problems by storing plan baselines that work over a period of time. Baselines have improved stability over outlines. Outlines will be desupported in a future release of SQL plan management. –Still supported in 11g.

41 41 Oracle OpenWorld 2009 SQL Baselines vs. Stored Outlines (cont.) –SQL Baselines vs. Stored Outlines Outlines are manually enabled and disabled. > You can think of them as being fixed. Baselines can be automatic or manual. Baselines are evaluated for better plans and used if that is the case. If you have a stored outline and the baseline finds a better plan, the evolve process must be performed to have the better plan used. > There is no conflict using both. > The query plan of the stored outline is the SQL plan baseline for this query.

42 42 Oracle OpenWorld 2009 Plan Management in Oracle11g Oracle records information about plans over time. Plan management behaves differently in 11g –A history of plans is kept only for repeatable SQL. –A statement log is kept for Oracle to see if SQL is repeated. –If a plan changes due to environmental issues, the new plan only is used if the optimizer deems it an improvement over the existing one. Plans can be captured manually or automatically. –These are not mutually exclusive. –Manual capture can complement Automatic capture.

43 43 Oracle OpenWorld 2009 Baselines: capturing manually and automatically Automatic Capture –Baselines captured automatically with init.ora parm optimizer_capture_sql_plan_baselines set to true. Default is false. –Plan history is created and kept. Info such as: sql_text, environment, outline, bind variables. –First plan use is kept as the baseline and history. –All future plans go to plan history. –Plans deemed to not cause performance degradation are added to the Baseline. This is part of plan evolution.

44 44 Oracle OpenWorld 2009 Baselines: capturing manually and automatically Manual Capture –Existing plans for SQL statements can be loaded as Baselines. To new or existing baselines. –Not verified by Oracle for performance. –Plans can be loaded from: SQL Tuning Sets AWR snapshots Cursor cache

45 45 Oracle OpenWorld 2009 Baselines: capturing manually and automatically Manual Capture using SQL Tuning Sets (sts) –Use function dbms_spm.load_plans_from_sqlset Loads the plans from a named tuning set. –e.g. to load plans from sql tuning set month_end SQL> declare mthend pls_integer; begin mthend := dbms_spm.load_plans_from_sqlset (sqlset_name => month_end); end; /

46 46 Oracle OpenWorld 2009 Baselines: capturing manually and automatically Manual Capture using AWR –To use AWR snapshots, load the plans into a SQL Tuning Set and then follow the steps to capture plans from the STS. –Example: To load plans from a SQL Tuning Set, do the following: > In OEM, go to Performance > choose the SQL Tuning Sets option > choose create > enter your criteria

47 47 Oracle OpenWorld 2009 Manual capture with STS in OEM - choose SQL Tuning Sets

48 48 Oracle OpenWorld 2009 Manual capture with STS in OEM - choose Create

49 49 Oracle OpenWorld 2009 Manual capture with STS in OEM - enter the creation options then choose next

50 50 Oracle OpenWorld 2009 Manual capture with STS in OEM - determine the load method then choose next

51 51 Oracle OpenWorld 2009 Manual capture with STS in OEM - enter the filter options then next

52 52 Oracle OpenWorld 2009 Manual capture with STS in OEM - enter job info and schedule then next

53 53 Oracle OpenWorld 2009 Manual capture with STS in OEM - show the SQL and review then Submit

54 54 Oracle OpenWorld 2009 Manual capture with STS in OEM - confirmation that this was successful

55 55 Oracle OpenWorld 2009 Manual capture with STS in OEM - now load the plan You have the SQL Tuning Set that can be loaded. Use dbms_spm.load_plans_from sqlset

56 56 Oracle OpenWorld 2009 Baselines: capturing manually and automatically Manual Capture using Cursor Cache –Get the SQL in cache as shown in the previous section. Use the SQL_Text or the SQL_ID. –Use function dbms_spm.load_plans_from_cursor_cache Loads the plans from named SQL. –e.g. to load a single plan from SQL cursor cache: Get the sql_id from v$sql as shown in part 1. SQL> declare csr_plan pls_integer; begin csr_plan := dbms_spm.load_plans_from_cursor_cache (sql_id => 36k6xhn2zmv3q1 ); end; /

57 57 Oracle OpenWorld 2009 Baselines: Evolving Automatically Steps to accept plans and add them to a baseline. 1.Set optimizer_use_sql_plan_baselines to true. 2.When SQL is compiled, the optimizer finds the best cost plan. 3.A search is then done for a matching plan in the baseline. If a match is found, the optimizer continues with that plan. If no match is found, the optimizer takes the plan with the lowest cost from the already accepted plans in the SQL plan baseline. 4.The best-cost plan found by the optimizer that does not match any baseline plans, is added to the SQL plan history as a non-accepted plan. This is a new plan. This is not used unless it can improve performance. Could be used in the future if a change to the system or to an object (e.g. index change) means already accepted plans cannot be recreated. In this case, Oracle will pick the best plan available.

58 58 Oracle OpenWorld 2009 Baselines: Evolving Automatically (cont.) Evolving plans using baselines and manual plan loading. The plan baseline provides alternative backup approaches that can be used by the optimizer. Constant improvement: the performance of new plans is being evaluated continually. –These are integrated into SQL plan baselines to evolve plans with better performance. –New plans are added to plan history as non-accepted plans. –The plans in plan history that are verified to not cause performance regression are accepted. –If a new plan is not worse than the SQL plan baseline performance, it becomes an accepted plan and integrates into the SQL baseline.

59 59 Oracle OpenWorld 2009 Evolving plans using baselines and manual plan loading. New Plan Add to History (non-accepted plan) Verify: cost is the same or better than baseline If true, then an accepted plan and added to the baseline Successful verification comes when the new plan performs better than the baseline. Baselines: Evolving Automatically (cont.)

60 60 Oracle OpenWorld 2009 Evolving plans manually. Plans can be evolved manually from cursor cache, sql tuning sets and the awr repository. Specify a specific SQL plan to add to plan history of the baseline and accept it if it performs better. –exec dbms_spm.evolve_sql_plan_baselines function If the new plan will perform better than the plan chosen from the baseline, its then accepted. Baselines: Evolving Manually

61 61 Oracle OpenWorld 2009 DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE ( sql_handle IN VARCHAR2 := NULL, -- can use a handle plan_name IN VARCHAR2 := NULL, -- or, can use a plan name time_limit IN INTEGER := DBMS_SPM.AUTO_LIMIT, -- in minutes verify IN VARCHAR2 := 'YES', -- perform a verify test on non- accepted plans. commit IN VARCHAR2 := 'YES') -- accept it if plan is better than the baseline RETURN CLOB; sql_handle:sql statement id. Null to consider all statements with non-accepted plans in their SQL plan baselines (in the sql management base) plan_name: Plan id. Default null considers all non-accepted plans in the sql plan baseline of either the identified sql statement or all sql statements if sql_handle is null time_limit: In minutes. Applies if verify=YES (default). Used as total time limit for all non-accepted plan verification. Can use dbms_spm_auto_limit (default) to allow the system to choose based on number of plan verifications to be done. Can also use dbms_spm_no_limit or you can also set a number of minutes. Baselines: Evolving Manually (cont.)

62 62 Oracle OpenWorld 2009 Second form below is used for a list of plans. DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE ( plan_list IN DBMS_SPM.NAME_LIST, -- list of plan names time_limit IN INTEGER := DBMS_SPM.AUTO_LIMIT, -- default & system chooses verify IN VARCHAR2 := 'YES', commit IN VARCHAR2 := 'YES') RETURN CLOB; Plan_list: Each plan can be the same or different sql statements –DBMS_SPM.NAME_LIST is a defined data type as table varchar2(30) Verify: execute a plan baseline and run a non-accepted plan. If better, change non-accepted to accepted. Verify=NO does not execute the plan but changes non-accepted to accepted if it is deemed better. Commit: update accepted status of non-accepted plans from No to Yes Baselines: Evolving Manually (cont.)

63 63 Oracle OpenWorld 2009 Baselines: fixed and non-fixed Fixed plans A baseline is fixed if it has one or more plans with the fixed attribute set to yes. Can be used to fix a plan for an SQL statement. –Can also migrate a stored outline and load it as a fixed plan. The optimizer will choose a fixed plan with the lowest cost over a non-fixed plan –Even if the non-fixed plan has a lower cost estimate. –If the fixed plan cannot be reproduced, then the best non- fixed plan will be used.

64 64 Oracle OpenWorld 2009 Baselines: fixed and non-fixed Fixed plans New plans will not be added to a fixed plan baseline. –Not evolved when dbms_spm.evolve_sql_plan_baseline run. –But, manually evolved when plans loaded from cursor cache or STS When using the sql tuning advisor: –When an sql profile is accepted and added to a fixed baseline, the plan is added as non-fixed. –To use the plan, manually alter the plan and set the fixed attribute to yes.

65 65 Oracle OpenWorld 2009 Baselines: Viewing Baselines Use proc. dbms_xplan.display_sql_plan_baseline –Can get the sql_handle from dba_sql_plan_baselines or sql$text. select * from table(dbms_xplan.display_sql_plan_baseline( sql_handle=>SYS_SQL_ , -- SQL whose plans will be displayed plan_name=> ….. -- specify a specific plan name format=>basic); -- basic or typical or all Example: to display all plans for an sql handle: Select p.* from table(dbms_xplan.display_sql_plan_baselines( SYS_SQL_123abc456defg789)) p; Example: to display all plans based on sql_text Select p.* from (select distinct sql_handle from dba_sql_plan_baselines where sql_text like CUSTOMER%) b, table(dbms_xplan.display_sql_plan_baseline(b.sql_handle, null, BASIC)) p;

66 66 Oracle OpenWorld 2009 Baselines: Viewing Baselines Example SQL> select p.* from table (dbms_xplan.display_sql_plan_baseline ( 'SYS_SQL_8bbad99f1c0631b0 ')) p; PLAN_TABLE_OUTPUT SQL handle: SYS_SQL_8bbad99f1c0631b0 SQL text: select empno from scott.emp where empno=7369 Plan name: SYS_SQL_PLAN_1c0631b08bbcf177 Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE Plan hash value: | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | | 0 | SELECT STATEMENT | | 1 | 4 | 0 (0) | 00:00:01 | |* 1 | INDEX UNIQUE SCAN| PK_EMP | 1 | 4 | 0 (0) | 00:00:01 | Predicate Information (identified by operation id): 1 - access("EMPNO"=7369) 24 rows selected.

67 67 Oracle OpenWorld 2009 Baselines: Viewing Baselines Example Alternatively, you can get a similar result –but will not include the predicate information using the following: SQL > Select p.* from (select distinct sql_handle from dba_sql_plan_baselines where lower(sql_text) like 'select empno from scott.emp where empno=7369%') b, table(dbms_xplan.display_sql_plan_baseline(b.sql_handle, null, 'BASIC')) p;

68 68 Oracle OpenWorld 2009 Baselines: moving to other DBs (can also use this for an Upgrade) To upgrade from 10g to 11g – high level overview: –In 10g, create an SQL Tuning Set (STS) –Export the STS –Upgrade to 11g –Import the file –Use dbms_spm.unpack_stgtab_baseline The old execution plans are now stored as baselines

69 69 Oracle OpenWorld 2009 Baselines: moving to other DBs (cont.) Example Baselines can be moved using Data Pump or Export/Import. Use the dbms_spm package Overview of the steps –Create a staging table –Pack the baselines that you want from the SQL Management Base (SMB) to the staging table. –Export the data from the staging table. –Transfer the file to the receiving system –Import the staging table. –Unpack the data from the staging table into the SMB at the new database.

70 70 Oracle OpenWorld First create a staging table use package dbms_spm.create_stgtab_baseline that will be used to to pack and unpack the SQL plan baselines. DBMS_SPM.CREATE_STGTAB_BASELINE ( table_name IN VARCHAR2, table_owner IN VARCHAR2 := NULL, tablespace_name IN VARCHAR2 := NULL); Baselines: moving to other DBs (cont.)

71 71 Oracle OpenWorld 2009 Baselines: moving to other DBs (cont.) For Example: create staging table blstage begin dbms_spm. create_stgtab_baseline( table_name => blstage, table_owner => OWN1, tablespace_name => TS1); end; /

72 72 Oracle OpenWorld Pack the baselines with many possible different criteria. DBMS_SPM.PACK_STGTAB_BASELINE ( table_name IN VARCHAR2, table_owner IN VARCHAR2 := NULL, sql_handle IN VARCHAR2 := NULL, plan_name IN VARCHAR2 := NULL, sql_text IN CLOB := NULL, creator IN VARCHAR2 := NULL, origin IN VARCHAR2 := NULL, enabled IN VARCHAR2 := NULL, accepted IN VARCHAR2 := NULL, fixed IN VARCHAR2 := NULL, module IN VARCHAR2 := NULL, action IN VARCHAR2 := NULL) RETURN NUMBER; Baselines: moving to other DBs (cont.)

73 73 Oracle OpenWorld Pack all enabled plans from user Scott to the staging table. Example: declare stgplans number; begin stgplans := dbms_spm.pack_stgtab_baseline( table_name => blstage, enabled => yes, creator => SCOTT); end; / Baselines: moving to other DBs (cont.)

74 74 Oracle OpenWorld Use Data Pump to exp table blstage. - You can also use the older export utility 4. Move the exported file to the other server (if needed) and import it to another DB 5. Use Data Pump to imp the blstage table to the new database. - You can also use the older import utility Baselines: moving to other DBs (cont.)

75 75 Oracle OpenWorld Unpack the staging table blstage into the SMB using package dbms_spm.unpack_stgtab_baseline. Package syntax is below: DBMS_SPM.UNPACK_STGTAB_BASELINE ( table_name IN VARCHAR2, table_owner IN VARCHAR2 := NULL, sql_handle IN VARCHAR2 := NULL,plan_name IN VARCHAR2 := NULL, sql_text IN CLOB := NULL,creator IN VARCHAR2 := NULL, origin IN VARCHAR2 := NULL,enabled IN VARCHAR2 := NULL, accepted IN VARCHAR2 := NULL,fixed IN VARCHAR2 := NULL, module IN VARCHAR2 := NULL,action IN VARCHAR2 := NULL) RETURN NUMBER; Baselines: moving to other DBs (cont.)

76 76 Oracle OpenWorld Unpack the baseline (cont.): Example: unpack all fixed baselines in staging table blstage declare stgplans number; begin stgplans := dbms_spm.unpack_stgtab_baseline( table_name => blstage, fixed => yes); end; / You are now done! Baselines: moving to other DBs (cont.)

77 77 Oracle OpenWorld 2009 SQL Baseline Example Show and set parameters SQL> sho parameter baseline NAME TYPE VALUE optimizer_capture_sql_plan_baselines booleanFALSE optimizer_use_sql_plan_baselines boolean TRUE SQL> alter system set optimizer_capture_sql_plan_baselines = true scope = both; System altered. SQL> sho parameter baseline NAME TYPE VALUE optimizer_capture_sql_plan_baselines boolean TRUE optimizer_use_sql_plan_baselines boolean TRUE

78 78 Oracle OpenWorld 2009 SQL Baseline Example (cont.) Showing baselines captured To view the baselines: SQL> select count(*) from dba_sql_plan_baselines; COUNT(*) 6 SQL> / COUNT(*) 8 SQL> / COUNT(*) 8 SQL> / COUNT(*) 9

79 79 Oracle OpenWorld 2009 Use OEM, go to Server & choose SQL Plan Control

80 80 Oracle OpenWorld 2009 Select the SQL Plan Baseline tab at the top of page. See below that plans not used for 53 weeks will be purged. Enter your SQL into the search string and press Go.

81 81 Oracle OpenWorld 2009 SQL Baseline example On the previous slide you will see the following: Parms Capture SQL Plan Baselines and Use SQL Plan Baselines are set to true. Retention weeks are set to 53 – the default. Ive entered search text into the SQL Text field. All baselined plans shown have been Enabled are can be considered. All plans have been Accepted and are therefore acceptable plans for a query. None of the plans are marked as Fixed, so there are no fixed plans that the optimizer would only consider. All plans will be Auto Purged after 53 days.

82 82 Oracle OpenWorld 2009 Your SQL shows up based on entered sql text: SQL> Select count(*) from dba_sql_plan_baselines;

83 83 Oracle OpenWorld 2009 Click on the SQL to get the plan details. Hit Return once youve viewed the plan

84 84 Oracle OpenWorld 2009 You now have options to deal with this baseline Select the plan (bottom left) and click Evolve (if the plan is not yet accepted).

85 85 Oracle OpenWorld 2009 Choose verify performance to compare this to the existing baseline for the query. Click OK

86 86 Oracle OpenWorld 2009 We see that this is already an accepted plan and that no SQL Plan Baselines required processing.

87 87 Oracle OpenWorld 2009 You can change the status with package dbms_spm If the plan shown on the previous slide was not accepted, you can change it as follows: declare spb binary_integer; begin spb := dbms.spm.alter_sql_plan_baseline ( sql_handle => SYS_SQL_a0b12c34d , plan_name => SYS_SQL_PLAN_7b33b11994d46ac6, attribute_name => ACCEPTED, attribute_value => NO ); end; /

88 88 Oracle OpenWorld 2009 The DBMS_SPM package contains 9 subprograms to manage baselines. alter_sql_plan_baseline function –Change an attribute of a plan or plans associated with an SQL statement. configure procedure –SQL Management Base (SMB) configuration options create_stgtab_baseline procedure –Create a staging table to move baselines to another system. drop_sql_plan_baseline function evolve_sql_plan_baseline function DBMS_SPM Subprograms

89 89 Oracle OpenWorld 2009 load_plans_from_cursor_cache function –Loads one or more plans in the cursor cache for a SQL statement. load_plans_from_sqlset function –Loads 1 or more plans from a SQL Tuning Set (STS) into SQL plan baselines. pack_stgtab_baseline function –Packs (exports) sql plan baselines from SQL management Base (SMB) to a staging table. unpack_stgtab_baseline function –Imports the plans from the staging table to the SMB. DBMS_SPM Subprograms (cont.)

90 90 Oracle OpenWorld 2009 SQL Management Base (SMB) SQL Management Base (SMB) overview Contains –Statement logs –Plan histories –Plan baselines –SQL profiles Stored in sysaux tablespace (this TS must be available) Configured with auto space management (asm) enabled. –Allows weekly purge of unused plans and logs. Useful when upgrading to 11g to prevent plan regression.

91 91 Oracle OpenWorld 2009 SMB Maintenance Storage –Limit is set to 10% the size of sysaux by default. Can range from 1% to 50% Weekly process checks this and writes a warning to the alert log when this is exceeded. If full, either increase SMB space limit, or sysaux size or perform a purge of plan baselines or profiles. To change the percent limit: begin dbms_spm.configure(space_budget_percent,25); end;

92 92 Oracle OpenWorld 2009 SMB Maintenance (cont.) Storage and Purge policy –Can set retention weeks from 5 to 523 with default = 53 begin dbms_spm.configure(plan_retention_weeks,125); end; –Any plan unused for 53 weeks will be purged by default. Uses last_executed value in SMB –Check the config in view dba_sql_management_config SQL> Select parameter_name, parameter_value from dba_sql_management_config;

93 93 Oracle OpenWorld 2009 SMB Maintenance (cont.) Storage and Purge policy –Check the config in view dba_sql_management_config SQL> Select * from dba_sql_management_config; parameter_nameparameter_value last_modified modified_by space_budget_percent10 Plan_retention_weeks53

94 94 Oracle OpenWorld 2009 SMB Management Migrating your Stored Outlines to SQL Plan baselines –If you are using stored outlines and want to migrate to SQL plan baselines: You can do this with the using the DBMS_SPM package. Migrate stored outlines to baselines using one of: –DBMS_SPM.load_plans_from_cursor_cache –DBMS_SPM.load_plans_from_sqlset –After migration has been completed, disable or remove the stored outlines.

95 95 Oracle OpenWorld 2009 Part 2: SQL Plan Management Summary Wrap-up of Part 2 –Plan management behaves differently in 11g Oracle records information about plans over time. –SQL Baselines are an enhancement to stored outlines –Automated approaches simplify maintenance –Manual approaches may be used to complement automation –Baselines are evaluated for better plans and used if that is the case. SQL baselines can evolve over time.

96 96 Oracle OpenWorld 2009 Conclusion Storing historical plans and statistics can be used initially as a backup plan when problems occur. –useful with Oracle upgrades as well as application upgrades and for environment or object changes. Start with stored outlines in 10g Upgrade to baselines in 11g Tim Quinlan TLQ Consulting Inc.


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