1. Obtaining and Interpreting Execution Plans using DBMS_XPLAN David Kurtz Go-Faster Consultancy Ltd. david.kurtz@go-faster.co.uk www.go-faster.co.uk

2. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 2 Oracle Database Specialist –Independent consultant System Performance tuning –PeopleSoft ERP –Oracle RDBMS Book –www.psftdba.com Who Am I?

3. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 3 Resources If you can’t hear me say so now. Please feel free to ask questions as we go along. The presentation is available from Conference website www.go-faster.co.uk

4. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 4 My Motivation Performance problems are instinctively routed to the DBA SQL Trace can locate a database problem Execution plan will show you what Oracle is doing. Many problems are caused by ‘poor SQL’ I often have to rewrite the SQL.

5. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 5 Your Motivation How to ask your DBA the right questions. How to answer some of those questions yourself How to find out how the database is executing a problematic SQL statement

6. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 6 Caveat I cannot, in one session, cover everything you need to know. But I can give you enough to get started on your own.

7. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 7 DBA’s Chief Weapons in the Performance Fight Surprise and Fear –“Surprise! Surprise! The application runs slowly” –“I’m afraid I can’t do anything about it. It’s a problem with the application code.” It doesn’t have to be like this. with Development

8. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 8 Agenda SQL Trace Execution Plans –Explain Plan For –DBMS_XPLAN –AWR –Licensing

9. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 9 What is SQL trace? Oracle shadow process writes a file on the database server Trace file contains –User and recursive SQL statements –Execution plan, physical & logical reads –Timing information –Wait and bind information (optional)

10. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 10 What’s the advantage of SQL Trace? You know how long each statement took to execute –Not just an estimate of how long The execution plan is what really happened You can find out how long each line of an execution plan took to execute –So you know where in the plan the problem is located.

11. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 11 What’s the problem with SQL Trace? If you’re not the DBA: –The trace file is on the database server udump/bdump directories –It is usually only readable by members of the DBA group.

12. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 12 What’s the problem with SQL Trace? Reactive –Run process with trace and respond to what happened. And sometimes –You don’t get the execution plan because the plan is only written to the trace file when the cursor is closed.

13. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 13 Alternatives to Trace Explain Plan For DBMS_XPLAN Assumption: –You know which SQL statement is your problem!

14. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 14 Example: Two HR tables PS_NAMES Name Null? Type ----------------------- -------- ------------ EMPLID* NOT NULL VARCHAR2(11) NAME_TYPE NOT NULL VARCHAR2(3) EFFDT NOT NULL DATE EFF_STATUS NOT NULL VARCHAR2(1) COUNTRY_NM_FORMAT NOT NULL VARCHAR2(3) NAME NOT NULL VARCHAR2(50) … PS_DEPT_TBL Name Null? Type ----------------------- -------- ------------ SETID* NOT NULL VARCHAR2(5) DEPTID* NOT NULL VARCHAR2(10) EFFDT* NOT NULL DATE EFF_STATUS NOT NULL VARCHAR2(1) DESCR NOT NULL VARCHAR2(30) DESCRSHORT NOT NULL VARCHAR2(10) …

15. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 15 A sample SQL SELECTd.setid, d.deptid, d.descr, n.emplid, n.name FROMps_dept_tbl d, ps_names n WHEREd.effdt = ( SELECT MAX(d1.effdt) FROMps_dept_tbl d1 WHEREd1.setid = d.setid ANDd1.deptid = d.deptid ANDd1.effdt <= SYSDATE) ANDd.eff_status = 'A' ANDn.emplid = d.manager_id /

16. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 16 Explain Plan For Writes to plan_table table –This is the way we used to do it up to Oracle 8i EXPLAIN PLAN SET statement_id = 'TST‘ INTO plan_table FOR /

17. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 17 Explain Plan For Then you had to query the plan table SELECT id, parent_id, lpad(' ', 2*(level-1))||operation||' '||options||' '||object_name||' '|| decode(id, 0, 'Cost = '||position) query_plan FROM plan_table START WITH id = 0 AND statement_id = 'TST' CONNECT BY prior id = parent_id AND statement_id = 'TST' ;

18. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 18 Explain Plan For And you get an execution plan with a cost ID P Query Plan --- --- ------------------------------------------ 0 SELECT STATEMENT Cost = 13 1 0 NESTED LOOPS 2 1 HASH JOIN 3 2 TABLE ACCESS FULL PS_DEPT_TBL 4 2 VIEW VW_SQ_1 5 4 HASH GROUP BY 6 5 INDEX FAST FULL SCAN PS1DEPT_TBL 7 1 TABLE ACCESS BY INDEX ROWID PS_NAMES 8 7 INDEX RANGE SCAN PS_NAMES

19. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 19 Explain Plan For Then you had to query the plan table SELECT id, parent_id, lpad(' ', 2*(level-1))||operation||' '||options||' '||object_name||' '|| decode(id, 0, 'Cost = '||position) query_plan FROM plan_table START WITH id = 0 AND statement_id = 'TST' CONNECT BY prior id = parent_id AND statement_id = 'TST' ;

20. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 20 DBMS_XPLAN Oracle supplied package procedure –Documented in PL/SQL Package and Types Reference manual. DISPLAY – 9i DISPLAY_CURSOR – 10g DISPLAY_AWR -10g DISPLAY_SQLSET – 10g DISPLAY_SQL_PLAN_BASELINE – 11g

21. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 21 DBMS_XPLAN.DISPLAY Displays contents of the plan table –Most recently explained statement –Or a named statement Available in Oracle 9i –No licence restrictions

22. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 22 DBMS_XPLAN.DISPLAY Usage DBMS_XPLAN.DISPLAY ( table_name IN VARCHAR2 DEFAULT 'PLAN_TABLE', statement_id IN VARCHAR2 DEFAULT NULL, format IN VARCHAR2 DEFAULT 'TYPICAL', filter_preds IN VARCHAR2 DEFAULT NULL);

23. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 23 DBMS_XPLAN.DISPLAY Formats –BASIC: basic execution plan, no metrics –TYPICAL: default. Most of the relavent information –SERIAL: like typical, but without any parallel execution information –ALL: like typical but also include projection, alias and remote SQL. –ADVANCED: like all but also includes the OUTLINE Not in the Oracle 10g documentation, but it works on 10g

24. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 24 DBMS_XPLAN.DISPLAY SELECT * FROM table(dbms_xplan.display()); Autotrace in SQL*Plus 10 now uses dbms_xplan.

25. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 25 select * from table( dbms_xplan.display( null, null, 'TYPICAL')); Plan hash value: 454993881 -------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 2 | 176 | 13 (16)| 00:00:01 | | 1 | NESTED LOOPS | | 2 | 176 | 13 (16)| 00:00:01 | |* 2 | HASH JOIN | | 1 | 65 | 11 (19)| 00:00:01 | |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 330 | 14850 | 6 (0)| 00:00:01 | | 4 | VIEW | VW_SQ_1 | 660 | 13200 | 4 (25)| 00:00:01 | | 5 | HASH GROUP BY | | 660 | 13860 | 4 (25)| 00:00:01 | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 660 | 13860 | 3 (0)| 00:00:01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 2 | 46 | 2 (0)| 00:00:01 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 2 | | 1 (0)| 00:00:01 | -------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("D"."EFFDT"="VW_COL_1" AND SYS_OP_DESCEND("D"."EFFDT")=SYS_OP_DESCEND( "VW_COL_1") AND "SETID"="D"."SETID" AND "DEPTID"="D"."DEPTID") 3 - filter("D"."EFF_STATUS"='A') 6 - filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("EFFDT"))<=SYSDATE@! AND SYS_OP_DESCEND("EFFDT")>=SYS_OP_DESCEND(SYSDATE@!)) 8 - access("N"."EMPLID"="D"."MANAGER_ID")

26. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 26 More Formats `ROWS - if relevant, shows the number of rows estimated by the optimizer BYTES - if relevant, shows the number of bytes estimated by the optimizer COST - if relevant, shows optimizer cost information PARTITION - if relevant, shows partition pruning information PARALLEL - if relevant, shows PX information (distribution method and table queue information) PREDICATE - if relevant, shows the predicate section PROJECTION -if relevant, shows the projection section ALIAS - if relevant, shows the "Query Block Name / Object Alias" section REMOTE - if relevant, shows the information for distributed query (for example, remote from serial distribution and remote SQL) NOTE - if relevant, shows the note section of the explain plan

27. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 27 select * from table( dbms_xplan.display( null, null, 'TYPICAL,-BYTES')); Plan hash value: 454993881 ------------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Cost (%CPU)| Time | ------------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 2 | 13 (16)| 00:00:01 | | 1 | NESTED LOOPS | | 2 | 13 (16)| 00:00:01 | |* 2 | HASH JOIN | | 1 | 11 (19)| 00:00:01 | |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 330 | 6 (0)| 00:00:01 | | 4 | VIEW | VW_SQ_1 | 660 | 4 (25)| 00:00:01 | | 5 | HASH GROUP BY | | 660 | 4 (25)| 00:00:01 | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 660 | 3 (0)| 00:00:01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 2 | 2 (0)| 00:00:01 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 2 | 1 (0)| 00:00:01 | ------------------------------------------------------------------------------------ Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("D"."EFFDT"="VW_COL_1" AND SYS_OP_DESCEND("D"."EFFDT")=SYS_OP_DESCEND( "VW_COL_1") AND "SETID"="D"."SETID" AND "DEPTID"="D"."DEPTID") 3 - filter("D"."EFF_STATUS"='A') 6 - filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("EFFDT"))<=SYSDATE@! AND SYS_OP_DESCEND("EFFDT")>=SYS_OP_DESCEND(SYSDATE@!)) 8 - access("N"."EMPLID"="D"."MANAGER_ID")

28. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 28 select * from table( dbms_xplan.display( null, null, ‘ALL')); Additional Information Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$C772B8D1 3 - SEL$C772B8D1 / D@SEL$1 4 - SEL$683B0107 / VW_SQ_1@SEL$7511BFD2 5 - SEL$683B0107 6 - SEL$683B0107 / D1@SEL$2 7 - SEL$C772B8D1 / N@SEL$1 8 - SEL$C772B8D1 / N@SEL$1

29. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 29 Specify Query Block Names SELECT/*+QB_NAME(MAIN_QUERY)*/ d.setid, d.deptid, d.descr, n.emplid, n.name FROMps_dept_Tbl d, ps_names n WHEREd.effdt = ( SELECT /*+QB_NAME(DEPT_SUBQUERY)*/ MAX(d1.effdt) FROM ps_dept_tbl d1 WHERE d1.setid = d.setid AND d1.deptid = d.deptid AND d1.effdt <= SYSDATE ) ANDd.eff_status = 'A' ANDn.emplid = d.manager_id /

30. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 30 select * from table( dbms_xplan.display( null, null, ‘ALL')); Additional Information Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$3787FDDA 3 - SEL$3787FDDA / D@MAIN_QUERY 4 - SEL$71F31171 / VW_SQ_1@SEL$4A7F38AA 5 - SEL$71F31171 6 - SEL$71F31171 / D1@DEPT_SUBQUERY 7 - SEL$3787FDDA / N@MAIN_QUERY 8 - SEL$3787FDDA / N@MAIN_QUERY

31. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 31 select * from table( dbms_xplan.display( null, null, ‘ALL')); Additional Information Column Projection Information (identified by operation id): ----------------------------------------------------------- 1 - (#keys=0) "D"."SETID"[VARCHAR2,5], "D"."DEPTID"[VARCHAR2,10], "D"."DESCR"[VARCHAR2,30], "N"."EMPLID"[VARCHAR2,11], "N"."NAME"[VARCHAR2,50] 2 - (#keys=4) "D"."SETID"[VARCHAR2,5], "D"."DEPTID"[VARCHAR2,10], "D"."DESCR"[VARCHAR2,30], "D"."MANAGER_ID"[VARCHAR2,11] 3 - "D"."SETID"[VARCHAR2,5], "D"."DEPTID"[VARCHAR2,10], "D"."EFFDT"[DATE,7], "D"."DESCR"[VARCHAR2,30], "D"."MANAGER_ID"[VARCHAR2,11] 4 - "VW_COL_1"[DATE,7], "SETID"[VARCHAR2,5], "DEPTID"[VARCHAR2,10] 5 - (#keys=2) "D1"."SETID"[VARCHAR2,5], "D1"."DEPTID"[VARCHAR2,10], MAX(SYS_OP_UNDESCEND(SYS_OP_DESCEND("EFFDT")))[7] 6 - "D1"."SETID"[VARCHAR2,5], "D1"."DEPTID"[VARCHAR2,10], SYS_OP_DESCEND("EFFDT")[RAW,12] 7 - "N"."EMPLID"[VARCHAR2,11], "N"."NAME"[VARCHAR2,50] 8 - "N".ROWID[ROWID,10], "N"."EMPLID"[VARCHAR2,11]

32. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 32 select * from table( dbms_xplan.display( null, null, ‘ADVANCED')); An outline is a set of hints Outline Data ------------- /*+ BEGIN_OUTLINE_DATA INDEX(@"SEL$2" "D1"@"SEL$2" "PS_DEPT_TBL") USE_HASH(@"SEL$1" "N"@"SEL$1") LEADING(@"SEL$1" "D"@"SEL$1" "N"@"SEL$1") INDEX_FFS(@"SEL$1" "N"@"SEL$1" "PS0NAMES") FULL(@"SEL$1" "D"@"SEL$1") OUTLINE(@"SEL$1") OUTLINE(@"SEL$2") OUTLINE_LEAF(@"SEL$1") OUTLINE_LEAF(@"SEL$2") ALL_ROWS OPTIMIZER_FEATURES_ENABLE('10.2.0.1') IGNORE_OPTIM_EMBEDDED_HINTS END_OUTLINE_DATA */

33. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 33 DBMS_XPLAN.DISPLAY Filter Predicates –Applied to the plan table –Simply get a partial execution plan

34. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 34 select * from table( dbms_xplan.display(null, null, null, 'object_name like ''%DEPT%''')); Plan hash value: 454993881 ---------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---------------------------------------------------------------------------------------- |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 330 | 14850 | 6 (0)| 00:00:01 | |* 6 | INDEX FAST FULL SCAN| PS1DEPT_TBL | 660 | 13860 | 3 (0)| 00:00:01 | ---------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter("D"."EFF_STATUS"='A') 6 - filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("EFFDT"))<=SYSDATE@! AND SYS_OP_DESCEND("EFFDT")>=SYS_OP_DESCEND(SYSDATE@!))

35. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 35 SQL Developer Explain Plan

36. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 36 DBMS_XPLAN.DISPLAY Rolled-up cost of each operation –Estimate of time (converted from cost to time) –Number of rows returned from each operation. Remember this is an prediction of what will happen based upon the CBO statistics and not reality.

37. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 37 The problem with EXPLAIN PLAN It is the execution plan now in this session with the statistics and environment in force now. It may be what will happen next time the statement is executed, but it may not be what happened last time.

38. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 38 DBMS_XPLAN.DISPLAY_CURSOR Displays the execution plan of a cursor in the library cache –Based upon view V$SQL_PLAN_STATISTICS_ALL –A SQL Statement might have multiple execution plans So it is what happened – sort of

39. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 39 DBMS_XPLAN.DISPLAY_CURSOR Usage DBMS_XPLAN.DISPLAY_CURSOR( sql_id IN VARCHAR2 DEFAULT NULL, child_number IN NUMBER DEFAULT NULL, format IN VARCHAR2 DEFAULT 'TYPICAL');

40. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 40 DBMS_XPLAN.DISPLAY_CURSOR Get SQL ID –V$SQL –V$SQLAREA –V$OPEN_CURSOR –V$SESSION

41. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 41 select * from table( dbms_xplan.display_cursor( 'bh01rt8q2820q')); PLAN_TABLE_OUTPUT ------------------------------------------------------- SQL_ID bh01rt8q2820q, child number 0 ------------------------------------- SELECT d.setid, d.deptid, d.descr, n.emplid, n.name FROM ps_dept_Tbl d, ps_names n WHERE d.effdt = ( SELECT MAX(d1.effdt) FROM ps_dept_tbl d1 WHERE d1.setid = d.setid AND d1.deptid = d.deptid AND d1.effdt <= SYSDATE ) AND d.eff_status ='A' AND n.emplid = d.manager_id …

42. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 42 Plan hash value: 454993881 -------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 13 (100)| | | 1 | NESTED LOOPS | | 2 | 176 | 13 (16)| 00:00:01 | |* 2 | HASH JOIN | | 1 | 65 | 11 (19)| 00:00:01 | |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 330 | 14850 | 6 (0)| 00:00:01 | | 4 | VIEW | VW_SQ_1 | 660 | 13200 | 4 (25)| 00:00:01 | | 5 | HASH GROUP BY | | 660 | 13860 | 4 (25)| 00:00:01 | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 660 | 13860 | 3 (0)| 00:00:01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 2 | 46 | 2 (0)| 00:00:01 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 2 | | 1 (0)| 00:00:01 | -------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("D"."EFFDT"="VW_COL_1" AND SYS_OP_DESCEND("D"."EFFDT")=SYS_OP_DESCEND( "VW_COL_1") AND "SETID"="D"."SETID" AND "DEPTID"="D"."DEPTID") 3 - filter("D"."EFF_STATUS"='A') 6 - filter((SYS_OP_UNDESCEND("D1"."SYS_NC00051$")<=SYSDATE@! AND "D1"."SYS_NC00051$">=SYS_OP_DESCEND(SYSDATE@!))) 8 - access("N"."EMPLID"="D"."MANAGER_ID") select * from table( dbms_xplan.display_cursor( 'bh01rt8q2820q'));

43. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 43 DBMS_XPLAN.DISPLAY_CURSOR The execution plan is the one that was used to execute the statement –But the costs and metrics are still based upon the CBO statistics –There may be a discrepancy between estimated and actual cost of operations in the plan

44. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 44 Descending and Function-Based Indexes SELECT uic.index_name, uic.column_name, uic.descend, uie.column_expression FROM user_ind_Columns uic, user_ind_expressions uie WHERE uic.column_name = 'SYS_NC00051$' AND uic.index_name = 'PS1DEPT_TBL' AND uie.index_name = uic.index_name AND uie.table_name = uic.table_name / INDEX_NAME COLUMN_NAME DESCEND COLUMN_EXPRESSION ------------ ------------ ------- ----------------- PS1DEPT_TBL SYS_NC00051$ DESC "EFFDT"

45. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 45 Extra Format Options IOSTAT: assumes basic statistics are collected when SQL executed MEMSTATS: if PGA management enable display memory management stats ALLSTATS: IOSTATS and MEMSTATS LAST: last execution only

46. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 46 Collecting Execution Statistics Hint one statement /*+ gather_plan_statistics */ Set for session ALTER SESSION SET statistics_level = 'ALL'

47. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 47 select * from table(dbms_xplan.display_cursor( ' fz3qdn0z07n8n ',null,'IOSTATS')); SQL_ID fz3qdn0z07n8n, child number 0 ------------------------------------- SELECT /*+ gather_plan_statistics */ d.setid, d.deptid, d.descr, n.emplid, n.name FROM ps_dept_Tbl d ps_names n WHERE d.effdt = ( SELECT MAX(d1.effdt) FROM ps_dept_tbl d1 WHERE d1.setid = d.setid AND d1.deptid = d.deptid AND d1.effdt <= SYSDATE ) AND d.eff_status = 'A' AND n.emplid = d.manager Plan hash value: 454993881 ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | ---------------------------------------------------------------------------------------------------- | 1 | NESTED LOOPS | | 1 | 2 | 65 |00:00:00.01 | 793 | |* 2 | HASH JOIN | | 1 | 1 | 618 |00:00:00.01 | 40 | |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 1 | 330 | 658 |00:00:00.01 | 23 | | 4 | VIEW | VW_SQ_1 | 1 | 660 | 620 |00:00:00.01 | 17 | | 5 | HASH GROUP BY | | 1 | 660 | 620 |00:00:00.01 | 17 | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 1 | 660 | 660 |00:00:00.01 | 17 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 618 | 2 | 65 |00:00:00.01 | 753 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 618 | 2 | 65 |00:00:00.01 | 691 | ----------------------------------------------------------------------------------------------------

48. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 48 select * from table(dbms_xplan.display_cursor( ' fz3qdn0z07n8n ',null,'MEMSTATS')); SQL_ID fz3qdn0z07n8n, child number 0 ------------------------------------- SELECT /*+ gather_plan_statistics */ d.setid, d.deptid, d.descr, n.emplid, n.name FROM ps_dept_Tbl d ps_names n WHERE d.effdt = ( SELECT MAX(d1.effdt) FROM ps_dept_tbl d1 WHERE d1.setid = d.setid AND d1.deptid = d.deptid AND d1.effdt <= SYSDATE ) AND d.eff_status = 'A' AND n.emplid = d.manager Plan hash value: 454993881 ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | OMem | 1Mem | O/1/M ---------------------------------------------------------------------------------------------------- | 1 | NESTED LOOPS | | 1 | 2 | 65 |00:00:00.01 | | | | |* 2 | HASH JOIN | | 1 | 1 | 618 |00:00:00.01 | 746K| 746K| 1/0/0| |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 1 | 330 | 658 |00:00:00.01 | | | | 4 | VIEW | VW_SQ_1 | 1 | 660 | 620 |00:00:00.01 | | | | | 5 | HASH GROUP BY | | 1 | 660 | 620 |00:00:00.01 | | | | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 1 | 660 | 660 |00:00:00.01 | | | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 618 | 2 | 65 |00:00:00.01 | | | |* 8 | INDEX RANGE SCAN | PS_NAMES | 618 | 2 | 65 |00:00:00.01 | | | | ----------------------------------------------------------------------------------------------------

49. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 49 MEMSTATS Columns 0Mem : The estimated amount of memory needed for an optimal execution 1Mem : The estimated amount of memory needed for one-pass execution. 0/1/M : Then number of times the execution was performed in optimal/one- pass/multipass mode.

50. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 50 DBMS_XPLAN.DISPLAY_AWR Displays the execution plan of a cursor stored in the Automatic Workload Repository (AWR) Extracts information from AWR tables –DBA_HIST_SQL_PLAN –DBA_HIST_SQLTEXT

51. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 51 DBMS_XPLAN.DISPLAY_AWR AWR is the replacement to Statspack –It is licensed as a part of Diagnostic Pack –Therefore, use of this function is similarly licensed. Statspack doesn’t report SQL_IDs

52. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 52 Statspack and DBMS_XPLAN select * from table( dbms_xplan.display( 'stats$sql_plan',null, 'all', 'hash_value = 740558870 and snap_id=4200')) If you use 10g STATSPACK, use hash_value, not plan_hash_value

53. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 53 DBMS_XPLAN.DISPLAY_AWR Usage DBMS_XPLAN.DISPLAY_AWR( sql_id IN VARCHAR2, plan_hash_value IN NUMBER DEFAULT NULL, db_id IN NUMBER DEFAULT NULL, format IN VARCHAR2 DEFAULT TYPICAL);

54. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 54

55. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 55 select * from table( dbms_xplan.display_awr( 'bh01rt8q2820q')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------------------- SQL_ID bh01rt8q2820q -------------------- SELECT d.setid, d.deptid, d.descr, n.emplid, n.name FROM ps_dept_Tbl d, ps_names n WHERE d.effdt = ( SELECT MAX(d1.effdt) FROM ps_dept_tbl d1 WHERE d1.setid = d.setid AND d1.deptid = d.deptid AND d1.effdt <= SYSDATE ) AND d.eff_status = 'A' AND n.emplid = d.manager_id Plan hash value: 454993881 -------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 13 (100)| | | 1 | NESTED LOOPS | | 2 | 176 | 13 (16)| 00:00:01 | | 2 | HASH JOIN | | 1 | 65 | 11 (19)| 00:00:01 | | 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 330 | 14850 | 6 (0)| 00:00:01 | | 4 | VIEW | VW_SQ_1 | 660 | 13200 | 4 (25)| 00:00:01 | | 5 | HASH GROUP BY | | 660 | 13860 | 4 (25)| 00:00:01 | | 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 660 | 13860 | 3 (0)| 00:00:01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 2 | 46 | 2 (0)| 00:00:01 | | 8 | INDEX RANGE SCAN | PS_NAMES | 2 | | 1 (0)| 00:00:01 | --------------------------------------------------------------------------------------------

56. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 56 Multiple Execution plans SQL_ID bxu9sk3q91trn -------------------- INSERT INTO TMP_ACTSEARCH1 (ACTIVITY_PK) SELECT ACT.ACTIVITY_PK FROM TBL_TMX_ACTIVITY ACT WHERE CONTAINS(ACT.ACTIVITYDESC, :B1 ) > 0 Plan hash value: 2274164979 -------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------- | 0 | INSERT STATEMENT | | | | 379K(100)| | | 1 | TABLE ACCESS FULL| TBL_TMX_ACTIVITY | 1 | 74 | 379K (8)| 00:00:30 | -------------------------------------------------------------------------------------- SQL_ID bxu9sk3q91trn -------------------- INSERT INTO TMP_ACTSEARCH1 (ACTIVITY_PK) SELECT ACT.ACTIVITY_PK FROM TBL_TMX_ACTIVITY ACT WHERE CONTAINS(ACT.ACTIVITYDESC, :B1 ) > 0 Plan hash value: 4216380757 -------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| -------------------------------------------------------------------------------------- | 0 | INSERT STATEMENT | | | | 1 (100)| | 1 | TABLE ACCESS BY INDEX ROWID| TBL_TMX_ACTIVITY | 1 | 73 | 0 (0)| | 2 | DOMAIN INDEX | FT_TABLE_RAJLCU1R | | | 0 (0)| --------------------------------------------------------------------------------------

57. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 57 DBMS_XPLAN.DISPLAY_SQLSET Displays execution plan of a statement in a tuning set. –It is licensed as a part of Diagnostic Pack or Tuning Pack

58. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 58 DBMS_XPLAN.DISPLAY_SQLSET Usage DBMS_XPLAN.DISPLAY_SQLSET( sqlset_name IN VARCHAR2, sql_id IN VARCHAR2, plan_hash_value IN NUMBER NULL, format IN VARCHAR2 'TYPICAL', sqlset_owner IN VARCHAR2 NULL)

59. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 59 DBMS_XPLAN. DISPLAY_SQL_PLAN_BASELINE New in Oracle 11g Displays execution plan of a statement in a SQL base line. –It is licensed as a part of Tuning Pack(?)

60. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 60 DBMS_XPLAN. DISPLAY_SQL_PLAN_BASELINE Usage DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE ( sql_handle IN VARCHAR2 := NULL, plan_name IN VARCHAR2 := NULL, format IN VARCHAR2 := 'TYPICAL')

61. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 61 What is Wrong with this plan? ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | Cost (%CPU)| A-Rows | A-Time | Buffers | ---------------------------------------------------------------------------------------------------- | 1 | NESTED LOOPS | | 1 | 2 | 13 (16)| 65 |00:00:00.06 | 793 | |* 2 | HASH JOIN | | 1 | 1 | 11 (19)| 618 |00:00:00.04 | 40 | |* 3 | TABLE ACCESS FULL | PS_DEPT_TBL | 1 | 330 | 6 (0)| 658 |00:00:00.01 | | 4 | VIEW | VW_SQ_1 | 1 | 660 | 4 (25)| 620 |00:00:00.02 | 17 | | 5 | HASH GROUP BY | | 1 | 660 | 4 (25)| 620 |00:00:00.01 | 17 | |* 6 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 1 | 660 | 3 (0)| 660 |00:00:00.01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 618 | 2 | 2 (0)| 65 |00:00:00.02 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 618 | 2 | 1 (0)| 65 |00:00:00.01 | 691 ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("D"."EFFDT"="VW_COL_1" AND SYS_OP_DESCEND("D"."EFFDT")=SYS_OP_DESCEND( "VW_COL_1") AND "SETID"="D"."SETID" AND "DEPTID"="D"."DEPTID") 3 - filter("D"."EFF_STATUS"='A') 6 - filter((SYS_OP_UNDESCEND("D1"."SYS_NC00051$")<=SYSDATE@! AND "D1"."SYS_NC00051$">=SYS_OP_DESCEND(SYSDATE@!))) 8 - access("N"."EMPLID"="D"."MANAGER_ID")

62. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 62 Skewed distribution of Data SELECT eff_status, count(*) FROM ps_dept_tbl GROUP BY eff_status EFF COUNT(*) --- ---------- I 2 A 658

63. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 63 Collect Stats with Histograms This is the default option in 10g begin sys.dbms_stats.gather_table_stats (ownname=>'SYSADM',tabname=>'PS_DEPT_TBL',estimate_percent=>DBMS_STATS.AUTO_SAMPLE_SIZE,method_opt=>'FOR ALL COLUMNS SIZE AUTO',cascade=>TRUE); end; /

64. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 64 Any Better? ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | Cost (%CPU)| A-Rows | A-Time | Buffers | ---------------------------------------------------------------------------------------------------- | 1 | NESTED LOOPS | | 1 | 11 | 21 (10)| 65 |00:00:00.06 | 823 | |* 2 | HASH JOIN | | 1 | 5 | 11 (19)| 618 |00:00:00.04 | 70 | | 3 | VIEW | VW_SQ_1 | 1 | 660 | 4 (25)| 620 |00:00:00.01 | 17 | | 4 | HASH GROUP BY | | 1 | 660 | 4 (25)| 620 |00:00:00.01 | 17 | |* 5 | INDEX FAST FULL SCAN | PS1DEPT_TBL | 1 | 660 | 3 (0)| 660 |00:00:00.01 | |* 6 | TABLE ACCESS FULL | PS_DEPT_TBL | 1 | 658 | 6 (0)| 658 |00:00:00.01 | | 7 | TABLE ACCESS BY INDEX ROWID| PS_NAMES | 618 | 2 | 2 (0)| 65 |00:00:00.02 | |* 8 | INDEX RANGE SCAN | PS_NAMES | 618 | 2 | 1 (0)| 65 |00:00:00.01 | 691 ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("D"."EFFDT"="VW_COL_1" AND SYS_OP_DESCEND("D"."EFFDT")=SYS_OP_DESCEND("VW_COL_1" ) AND "SETID"="D"."SETID" AND "DEPTID"="D"."DEPTID") 5 - filter((SYS_OP_UNDESCEND("D1"."SYS_NC00051$")<=SYSDATE@! AND "D1"."SYS_NC00051$">=SYS_OP_DESCEND(SYSDATE@!))) 6 - filter("D"."EFF_STATUS"='A') 8 - access("N"."EMPLID"="D"."MANAGER_ID")

65. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 65 The data is skewed 37 setids 435 departments 37 distinct managers 1.06 rows per setid & deptid 19 distinct effective dates.

66. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 66 Example: A SQL Problem You have identified your problem process… you have got your execution plan What do you do next? –(This example is based on SQL Trace and TKPROF)

67. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 67 SQL statement INSERT INTO PS_PP_CUST_TMP2 ( PROCESS_INSTANCE, DEPOSIT_BU, DEPOSIT_ID, PAYMENT_SEQ_NUM, CUST_ID, PAYMENT_AMT, PAYMENT_DT, PP_METHOD, SETID, SUBCUST_QUAL1, SUBCUST_QUAL2, PP_HOLD, PP_MET_SW, PAYMENT_CURRENCY ) SELECT DISTINCT P.PROCESS_INSTANCE, P.DEPOSIT_BU, P.DEPOSIT_ID, P.PAYMENT_SEQ_NUM, C.CUST_ID, P.PAYMENT_AMT, P.PAYMENT_DT, O.PP_METHOD, O.SETID, C.SUBCUST_QUAL1, C.SUBCUST_QUAL2, O.PP_HOLD, 'N', P.PAYMENT_CURRENCY FROM PS_CUST_OPTION O, PS_ITEM I, PS_CUSTOMER C, PS_SET_CNTRL_REC S, PS_PAYMENT_ID_ITEM X, PS_PP_PAYMENT_TMP P WHERE P.PROCESS_INSTANCE = 212 AND S.RECNAME = 'CUSTOMER' AND S.SETID = C.SETID AND S.SETCNTRLVALUE = I.BUSINESS_UNIT AND I.CUST_ID = C.CUST_ID AND I.ITEM_STATUS = 'O' AND O.SETID = C.REMIT_FROM_SETID AND O.CUST_ID = C.REMIT_FROM_CUST_ID AND O.EFFDT = ( SELECT MAX(Z.EFFDT) FROM PS_CUST_OPTION Z WHERE Z.SETID = O.SETID AND Z.CUST_ID = O.CUST_ID AND Z.EFF_STATUS = 'A' AND Z.EFFDT <= P.PAYMENT_DT ) AND O.PP_METHOD <> ' ' AND P.DEPOSIT_BU = X.DEPOSIT_BU AND P.DEPOSIT_ID = X.DEPOSIT_ID AND P.PAYMENT_SEQ_NUM = X.PAYMENT_SEQ_NUM AND X.REF_QUALIFIER_CODE = 'I' AND X.REF_VALUE = I.ITEM

68. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 68 Statistics … count = number of times OCI procedure was executed cpu = cpu time in seconds executing elapsed = elapsed time in seconds executing disk = number of physical reads of buffers from disk query = number of buffers gotten for consistent read current = number of buffers gotten in current mode (usually for update) rows = number of rows processed by the fetch or execute call … call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.31 0.33 4 0 4 0 Execute 1 156.61 160.23 164769 3981545 0 0 Fetch 0 0.00 0.00 0 0 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 2 156.92 160.56 164773 3981545 4 0

69. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 69 Execution plan Rows Execution Plan ------- --------------------------------------------------- 0 INSERT STATEMENT GOAL: CHOOSE 0 SORT (UNIQUE) 0 FILTER 0 NESTED LOOPS 8 NESTED LOOPS 1000040 NESTED LOOPS 360 NESTED LOOPS 10 NESTED LOOPS 10 TABLE ACCESS (BY INDEX ROWID) OF 'PS_PP_PAYMENT_TMP' 11 INDEX (RANGE SCAN) OF 'PSAPP_PAYMENT_TMP' (NON-UNIQUE) 20 INDEX (RANGE SCAN) OF 'PSAPAYMENT_ID_ITEM' (NON-UNIQUE) 360 TABLE ACCESS (BY INDEX ROWID) OF 'PS_SET_CNTRL_REC' 370 INDEX (RANGE SCAN) OF 'PSBSET_CNTRL_REC' (NON-UNIQUE) 1000040 TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUSTOMER' 1000400 INDEX (RANGE SCAN) OF 'PS#CUSTOMER' (NON-UNIQUE) 1000048 INDEX (RANGE SCAN) OF 'PS#ITEM' (NON-UNIQUE) 8 TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUST_OPTION' 16 INDEX (RANGE SCAN) OF 'PS_CUST_OPTION' (UNIQUE) 0 SORT (AGGREGATE) 0 TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUST_OPTION' 0 INDEX (RANGE SCAN) OF 'PS_CUST_OPTION' (UNIQUE)

70. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 70 1. Make the statement readable SELECT DISTINCT P.PROCESS_INSTANCE, P.DEPOSIT_BU, P.DEPOSIT_ID, P.PAYMENT_SEQ_NUM, C.CUST_ID, P.PAYMENT_AMT, P.PAYMENT_DT, O.PP_METHOD, O.SETID, C.SUBCUST_QUAL1, C.SUBCUST_QUAL2, O.PP_HOLD, 'N', P.PAYMENT_CURRENCY FROMPS_CUST_OPTION O, PS_ITEM I, PS_CUSTOMER C, PS_SET_CNTRL_REC S, PS_PAYMENT_ID_ITEM X, PS_PP_PAYMENT_TMP P WHEREP.PROCESS_INSTANCE = 212 AND S.RECNAME = 'CUSTOMER' AND S.SETID = C.SETID AND S.SETCNTRLVALUE = I.BUSINESS_UNIT AND I.CUST_ID = C.CUST_ID AND I.ITEM_STATUS = 'O' AND O.SETID = C.REMIT_FROM_SETID AND O.CUST_ID = C.REMIT_FROM_CUST_ID AND O.EFFDT = (SELECT MAX(Z.EFFDT) FROM PS_CUST_OPTION Z WHERE Z.SETID = O.SETID AND Z.CUST_ID = O.CUST_ID AND Z.EFF_STATUS = 'A' AND Z.EFFDT <= P.PAYMENT_DT) AND O.PP_METHOD <> ' ' AND P.DEPOSIT_BU = X.DEPOSIT_BU AND P.DEPOSIT_ID = X.DEPOSIT_ID AND P.PAYMENT_SEQ_NUM = X.PAYMENT_SEQ_NUM AND X.REF_QUALIFIER_CODE = 'I' AND X.REF_VALUE = I.ITEM

71. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 71 2. Start to draw the query PS_CUST_OPTION (O) PS_SET_CNTRL_REC (S) PS_PP_PAYMENT_TMP (P) PS_PAYMENT_ID_ITEM (X) PS_ITEM (I) PS_CUSTOMER (C) 3. Add the joins PROCESS_INSTANCE = 212 RECNAME = 'CUSTOMER' REF_QUALIFIER_CODE = 'I' I.ITEM_STATUS = 'O' SETIDCUST_ID O.SETID = C.REMIT_FROM_SETID O.CUST_ID = C.REMIT_FROM_CUST_ID S.SETCNTRLVALUE = I.BUSINESS_UNIT PP_METHOD <> ' ' X.REF_VALUE = I.ITEM P.DEPOSIT_BU = X.DEPOSIT_BU P.DEPOSIT_ID = X.DEPOSIT_ID P.PAYMENT_SEQ_NUM = X.PAYMENT_SEQ_NUM EFFDT

72. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 72 4. Get the order from the plan 0 FILTER 0 NESTED LOOPS 8 NESTED LOOPS 1000040 NESTED LOOPS 360 NESTED LOOPS 10 NESTED LOOPS 10 (1)TABLE ACCESS (BY INDEX ROWID) OF 'PS_PP_PAYMENT_TMP' 11 INDEX (RANGE SCAN) OF 'PSAPP_PAYMENT_TMP' (NON-UNIQUE) 20 (2)INDEX (RANGE SCAN) OF 'PSAPAYMENT_ID_ITEM' (NON-UNIQUE) 360 (3)TABLE ACCESS (BY INDEX ROWID) OF 'PS_SET_CNTRL_REC' 370 INDEX (RANGE SCAN) OF 'PSBSET_CNTRL_REC' (NON-UNIQUE) 1000040 (4)TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUSTOMER' 1000400 INDEX (RANGE SCAN) OF 'PS#CUSTOMER' (NON-UNIQUE) 1000048 (5)INDEX (RANGE SCAN) OF 'PS#ITEM' (NON-UNIQUE) 8 (6)TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUST_OPTION' 16 INDEX (RANGE SCAN) OF 'PS_CUST_OPTION' (UNIQUE) 0 SORT (AGGREGATE) 0 TABLE ACCESS (BY INDEX ROWID) OF 'PS_CUST_OPTION' INDEX (RANGE SCAN) OF 'PS_CUST_OPTION' (UNIQUE)

73. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 73 5. Put the order in the diagram PS_CUST_OPTION (O) PS_SET_CNTRL_REC (S) PS_PP_PAYMENT_TMP (P) PS_PAYMENT_ID_ITEM (X) PS_ITEM (I) PS_CUSTOMER (C) PROCESS_INSTANCE = 212 RECNAME = 'CUSTOMER' REF_QUALIFIER_CODE = 'I' I.ITEM_STATUS = 'O' SETIDCUST_ID O.SETID = C.REMIT_FROM_SETID O.CUST_ID = C.REMIT_FROM_CUST_ID S.SETCNTRLVALUE = I.BUSINESS_UNIT PP_METHOD <> ' ' X.REF_VALUE = I.ITEM P.DEPOSIT_BU = X.DEPOSIT_BU P.DEPOSIT_ID = X.DEPOSIT_ID P.PAYMENT_SEQ_NUM = X.PAYMENT_SEQ_NUM PS_PP_PAYMENT_TMP (P) 1 PS_PAYMENT_ID_ITEM (X) 2 PS_SET_CNTRL_REC (S) 3 PS_CUSTOMER (C) 4 PS_ITEM (I) 5 PS_CUST_OPTION (O) 6 EFFDT

74. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 74 6. This time, the answer is an index CREATE INDEX PSBITEM ON PS_ITEM (ITEM, CUST_ID, BUSINESS_UNIT, ITEM_STATUS) TABLESPACE PSINDEX STORAGE (INITIAL 10K NEXT 98K MAXEXTENTS 110 PCTINCREASE 0) /

75. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 75 New Execution Order PS_CUST_OPTION (O) PS_SET_CNTRL_REC (S) PS_PP_PAYMENT_TMP (P) PS_PAYMENT_ID_ITEM (X) PS_ITEM (I) PS_CUSTOMER (C) PROCESS_INSTANCE = 212 RECNAME = 'CUSTOMER' REF_QUALIFIER_CODE = 'I' I.ITEM_STATUS = 'O' SETIDCUST_ID O.SETID = C.REMIT_FROM_SETID O.CUST_ID = C.REMIT_FROM_CUST_ID S.SETCNTRLVALUE = I.BUSINESS_UNIT PP_METHOD <> ' ' X.REF_VALUE = I.ITEM P.DEPOSIT_BU = X.DEPOSIT_BU P.DEPOSIT_ID = X.DEPOSIT_ID P.PAYMENT_SEQ_NUM = X.PAYMENT_SEQ_NUM PS_PP_PAYMENT_TMP (P) 1 PS_PAYMENT_ID_ITEM (X) 2 PS_SET_CNTRL_REC (S) 4 PS_CUSTOMER (C) 5 PS_ITEM (I) 3 PS_CUST_OPTION (O) 6 EFFDT

76. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 76 Statistics Before call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.31 0.33 4 0 4 0 Execute 1 156.61 160.23 164769 3981545 0 0 Fetch 0 0.00 0.00 0 0 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 2 156.92 160.56 164773 3981545 4 0 After call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.35 2.56 3 0 3 0 Execute 1 0.03 0.05 38 289 3 0 Fetch 0 0.00 0.00 0 0 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 2 0.38 2.61 41 289 6 0

77. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 77 Conclusion Obtaining and understanding an execution plan is critical to understanding performance problems If you can get an execution plan –you can work out what Oracle has done with your SQL statement –Then you can decide how to resolve you performance problem

78. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 78 Acknowledgements 10g/11g DBMS_XPLAN –Carol Dacko, University of Michigan Collaborate 08 Conference presentation –Blog to be launched soon Rob van Wijk –http://rwijk.blogspot.com/2008/03/dbmsxplandi splaycursor.htmlhttp://rwijk.blogspot.com/2008/03/dbmsxplandi splaycursor.html

79. Questions?

80. Obtaining and Interpreting Execution Plans using DBMS_XPLAN David Kurtz Go-Faster Consultancy Ltd. david.kurtz@go-faster.co.uk www.go-faster.co.uk

81. Questions?

82. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 82 Acknowledgements 10g/11g DBMS_XPLAN –Carol Dacko, University of Michigan Collaborate 08 Conference presentation –Blog to be launched soon Rob van Wijk –http://rwijk.blogspot.com/2008/03/dbmsxplandi splaycursor.htmlhttp://rwijk.blogspot.com/2008/03/dbmsxplandi splaycursor.html

83. DBMS_XPLAN UKOUG2008 ©www.go-faster.co.uk 83 Conclusion Obtaining and understanding an execution plan is critical to understanding performance problems If you can get an execution plan –you can work out what Oracle has done with your SQL statement –Then you can decide how to resolve you performance problem