Downloaded 39 times
More Related Content
Similar to Combining ACS Flexibility with SPM Stability
Combining ACS Flexibility with SPM Stability
- 1. Combining Adap-ve Cursor Sharing (ACS) Flexibility with SQL Plan Management (SPM) Stability Carlos Sierra
- 2. Carlos Sierra • • • • • Consultant/Developer/DBA Oracle Performance SQLTXPLAIN (SQLT) SQL Tuning Tools Enkitec (c) 2014 2
- 3. Topics • • • • Plan Flexibility and Plan Stability Adap-ve Cursor Sharing (ACS) SQL Plan Management (SPM) Combining ACS and SPM Enkitec (c) 2014 3
- 4. Plan Flexibility • Cost-‐based Op-mizer (CBO) – Introduced in Oracle 7 – Computes an Op-mal Plan based on • Heuris-cs • Query Predicates • Schema Object Sta-s-cs • Several Others Enkitec (c) 2014 4
- 5. Flexibility: Good or Evil? • CBO Mission – Compute an Op-mal Plan for a given SQL and its Data • Plans have many and complex Dependencies • CBO Performance – Successful most of the -mes • Produces a sub-‐op-mal Plan some&mes Enkitec (c) 2014 5
- 6. DBA Recurrent Bad Dream • A business cri-cal process experiences an occasional slow down – Same SQL usually runs very quickly – Developers claim they haven’t changed anything – Users claim they do the same every -me – Business is sick and -red of repor-ng this to… YOU! Enkitec (c) 2014 6
- 7. Plan Performs Inconsistently? (1) • • • • • • Concurrency with some other Process State of Buffer Cache RAC Node Affinity CPU Starva-on Sudden Changes on Data Volume Inconsistent Performance through Database Link Enkitec (c) 2014 7
- 8. Plan Performs Inconsistently? (2) • • • • • Downgraded Parallel Execu-on Crossing Small-‐Table Threshold Resource Manager Direc-ve Plan Flips Many Others… Enkitec (c) 2014 8
- 9. WHY a Plan Flips? (1) • • • • • Bind Variable Peeking with Histograms Outdated Schema Object (SO) Sta-s-cs Missing SO Sta-s-cs Fresh SO Sta-s-cs New Empty Par--ons Enkitec (c) 2014 9
- 10. WHY a Plan Flips? (2) • Incomplete set of CBO Hints – Either on SQL Text or SQL Profile • Dropped, Invalid, Invisible or new Indexes • Index or Table rebuild • Two or more Plans with similar Cost Enkitec (c) 2014 10
- 11. WHY a Plan Flips? (3) • • • • Database Parameters Changes CBO System Sta-s-cs Changes Asynchronous SO Sta-s-cs Gathering Many Others… Enkitec (c) 2014 11
- 12. How to Mi-gate Plan Flipping • Sound CBO Sta-s-cs • Default CBO Parameters • Regulate Global Changes Enkitec (c) 2014 12
- 13. Plan Flexibility Allies • • • • • • CBO Parameters CBO Sta-s-cs Dynamic Sampling Cardinality Feedback Cursor Sharing Adap,ve Cursor Sharing (ACS) Enkitec (c) 2014 13
- 14. Plan Stability Tools • • • • CBO Hints Stored Outlines SQL Profiles SQL Plan Management (SPM) Enkitec (c) 2014 14
- 15. Cursor Sharing • Use of Bind Variables instead of Literals – AND p.prod_category LIKE 'Sooware%’ – AND p.prod_category LIKE :b5 • Goal: Reduce Hard Parsing – Improve Scalability • Reduce CPU u-liza-on • Reduce Shared Memory footprint Enkitec (c) 2014 15
- 16. Cursor Sharing Shortcomings • Flipping Plans – Exacerbated by Histograms on Skewed Data – AND c.cust_marital_status = :b2 • :b2 := ‘married’ • :b2 := ‘widow’ – Plan is computed at hard parse • Plan becomes a long term moving target Enkitec (c) 2014 16
- 17. Adap-ve Cursor Sharing (ACS) • 11g+ • Mul-ple Op-mal Plans per SQL – As per “Selec-vity” of Predicates • :b2 := ‘married’ (close to 60% maybe) • :b2 := ‘widow’ (this one is more selec-ve) Enkitec (c) 2014 17
- 18. ACS Challenges • Minimize Resources Impact – Monitor only a subset of SQL Statements – Ac-vate ACS only for a subset of the monitored SQL – Share Execu-ons Plans through a “Selec-vity Profile” Bind Aware ACS Bind Sensi-ve All Statements Enkitec (c) 2014 18
- 19. Becoming Bind Sensi-ve 1. SQL has Range Predicates on Bind Variables – AND c.cust_year_of_birth BETWEEN :b3 AND :b4 – AND p.prod_category LIKE :b5 2. SQL has Equality Predicates on Bind Variables and Column has a Histogram – AND c.cust_marital_status = :b2 – AND TO_CHAR(s.-me_id, 'YYYY') = :b6 Enkitec (c) 2014 19
- 20. Becoming Bind Aware 1. Rows Processed change substan-ally between Execu-ons – Between a few rows to millions 2. Rows Processed oscillate significantly between Execu-ons – Between a few rows and a few thousand – Between a few thousand and millions Enkitec (c) 2014 20
- 21. ACS Monitoring • V$SQL (State) – is_shareable – is_bind_sensi-ve – is_bind_aware • V$SQL_CS_STATISTICS (Rows Processed) • V$SQL_CS_HISTOGRAM (3 Buckets S/M/L) • V$SQL_CS_SELECTIVITY (Selec-vity Profile) Enkitec (c) 2014 21
- 22. Rows Processed • • • • v$sql_cs_sta-s-cs.rows_processed Updated only at hard parse A measure of amount of work on Execu-on Plan Three sizes: S/M/L – 0: Small – 1: Medium – 2: Large Enkitec (c) 2014 22
- 23. Rows Processed • • • • v$sql_cs_sta-s-cs.rows_processed Updated only at hard parse A measure of amount of work on Execu-on Plan Three sizes: S/M/L – 0: Small (less than 1K rows) – 1: Medium (between 1k and 1m rows) – 2: Large (more than 1m rows) Enkitec (c) 2014 23
- 24. ACS Buckets • v$sql_cs_histogram.bucket_id – 0: Small – 1: Medium – 2: Large • v$sql_cs_histogram.count – Incremented with each Execu-on as per • v$sql_cs_sta-s-cs.rows_processed Enkitec (c) 2014 24
- 25. Rows Processed and ACS Buckets IF v$sql_cs_statistics.rows_processed < 1K THEN v$sql_cs_histogram.count(0)++ ELSIF v$sql_cs_statistics.rows_processed < 1M THEN v$sql_cs_histogram.count(1)++ ELSE v$sql_cs_histogram.count(2)++ END IF Enkitec (c) 2014 25
- 26. Becoming Bind Aware 1. Small and Large buckets have a value – bucket_id.count(0) > 0 AND bucket_id.count(2) > 0 2. Two adjacent buckets have same non-‐zero value – bucket_id.count(0) = bucket_id.count(1) > 0 – bucket_id.count(1) = bucket_id.count(2) > 0 Enkitec (c) 2014 26
- 27. Rows Processed per Execu-on • • • • • • • 10(0)… 50(0)… 3,000,000(2)… BA 30(0)… 3,000(1)… BA 2,000,000(2)… 1(0)… BA 0(0)… 10,000(1)… BA 3,000(1)… 2,000(1)… 200(0)… 300(0)… BA 10… 100… 500… 2,000… 3,000… 5,000… BA rows_processed(bucket_id)… Bind Aware(BA) Enkitec (c) 2014 27
- 28. WHY becoming BA is important? • Mul-ple Op-mal Plans are created aoer Cursor becomes Bind Aware Enkitec (c) 2014 28
- 29. Sample Query (1) SELECT p.prod_subcategory_desc subcatagory, SUM(amount_sold) amount_sold FROM sh.customers c, sh.products p, sh.sales s WHERE c.cust_gender = 'M' AND c.cust_marital_status = 'single' AND c.cust_year_of_birth BETWEEN 1913 AND 1990 AND p.prod_category LIKE 'Software%' AND TO_CHAR(s.time_id, 'YYYY') = '2001' AND s.cust_id = c.cust_id AND s.prod_id = p.prod_id GROUP BY p.prod_subcategory_desc ORDER BY p.prod_subcategory_desc; Enkitec (c) 2014 29
- 30. Sample Query (2) • Based on Sample Schema SH – With CBO Histograms in all Columns • Not a requirement for this ACS test • • • • 3 Tables with Filter Predicates 2 Joins 6 possible Join Orders Several possible Execu-on Plans Enkitec (c) 2014 30
- 31. Demo 1 • 5 Execu-ons of Sample Query using Literals – Different values for each Execu-on • Sequence 1, 2, 3, 4 and 5 – Each Execu-on performs a Hard Parse – Each Execu-on computes a “new” Plan – Each seems to be an “Op-mal” Plan Enkitec (c) 2014 31
- 32. Demo 2 • 5 Execu-ons of Sample Query using Binds – Different values for each Execu-on • Sequence 1, 2, 3, 4 and 5 – Each Execu-on performs a Hard Parse • Forced with a Cursor Flush before the Execu-on – Each computes a “new” Op-mal Plan • Almost same as “with Literals” Enkitec (c) 2014 32
- 33. Demo 2 Results Query Rows Processed ACS Bucket Plan Hash Value 1 1,483,124 2 2048551027 2 1,272,154 2 3022804314 3 1,014,876 2 2326939410 4 716,168 1 2163719564 5 530 0 2163719564 Enkitec (c) 2014 33
- 34. Demo 3 • 5 Execu-ons of Sample Query using Binds – Different values for each Execu-on • Sequence 1, 2, 3, 4 and 5 – No Cursor Flush between Execu-ons – First Execu-on computes a “new” Op-mal Plan – All Execu-ons use same Plan… Enkitec (c) 2014 34
- 35. Demo 3 Results Query Rows Processed ACS Bucket Op,mal Plan ACS Aware Executed 1 1,483,124 2 2048551027 N 2048551027 2 1,272,154 2 3022804314 N 2048551027 3 1,014,876 2 2326939410 N 2048551027 4 716,168 1 2163719564 N 2048551027 5 530 0 2163719564 N 2048551027 Enkitec (c) 2014 35
- 36. Demo 4 • 5 Execu-ons of Sample Query using Binds – Different values for each Execu-on • Sequence 5, 4, 3, 2 and 1 – No Cursor Flush between Execu-ons – Cursor becomes Bind Aware aoer 2nd Execu-on – All Execu-ons used an Op-mal Plan Enkitec (c) 2014 36
- 37. Demo 4 Results Query Rows Processed ACS Bucket Op,mal Plan Bind Aware Executed 5 530 0 2163719564 N 2163719564 4 716,168 1 2163719564 N 2163719564 3 1,014,876 2 2326939410 Y 2326939410 2 1,272,154 2 3022804314 Y 3022804314 1 1,483,124 2 2048551027 Y 2048551027 Enkitec (c) 2014 37
- 38. Demo 5 • 5 Execu-ons of Sample Query using Binds – Different values for each Execu-on • Sequence 5, 1, 2, 3 and 4 – No Cursor Flush between Execu-ons – Cursor becomes Bind Aware aoer 2nd Execu-on – All but one Execu-ons used an Op-mal Plan Enkitec (c) 2014 38
- 39. Demo 5 Results Query Rows Processed ACS Bucket Op,mal Plan Bind Aware Executed 5 530 0 2163719564 N 2163719564 1 1,483,124 2 2048551027 N 2163719564 2 1,272,154 2 3022804314 Y 3022804314 3 1,014,876 2 2326939410 Y 2326939410 4 716,168 1 2163719564 Y 2163719564 Enkitec (c) 2014 39
- 40. Controlling ACS with CBO Hint • /*+ BIND_AWARE */ – Bypasses the monitoring phase of a Bind Sensi-ve SQL • /*+ NO_BIND_AWARE */ – Turns off ACS for given SQL Enkitec (c) 2014 40
- 41. Controlling ACS with SQL Patch • SYS.DBMS_SQLDIAG_INTERNAL.I_CREATE_PATCH – sql_text – hint_text => BIND_AWARE • Script sqlpch.sql Enkitec (c) 2014 41
- 42. ACS Plan Selec-on • On every Execu-on of Bind Aware Cursor – Compute Selec-vity of each qualifying Predicate – Search Selec-vity within Range of values on ACS Selec-vity Profile – If within Range, lookup Child Number and use its Plan – Else, Hard Parse and Execute newly computed Plan • If same as exis-ng Plan, then update Selec-vity Profile • Else, create Selec-vity Profile for new Child Number Enkitec (c) 2014 42
- 43. Selec-vity Profile (1) • v$sql_cs_selec-vity – predicate – range_id • low and high (selec-vi-es) – child_number Enkitec (c) 2014 43
- 44. Selec-vity Profile (2) CHILD PREDICATE RANGE_ID LOW HIGH -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ 1 <=B4 0 0.860941 1.052262 1 =B1 0 0.602369 0.736229 1 =B2 0 0.455337 0.556523 1 >=B3 0 0.182445 0.222988 1 B5 0 0.306250 0.374306 2 <=B4 0 0.892666 1.091036 2 =B1 0 0.297574 0.363702 2 =B2 0 0.455337 0.556523 2 >=B3 0 0.077947 0.095268 2 B5 0 0.306250 0.374306 3 <=B4 0 0.836835 1.022798 3 =B1 0 0.297574 0.363702 3 =B2 0 0.002085 0.002548 3 >=B3 0 0.221447 0.270657 3 B5 0 0.306250 0.374306 Enkitec (c) 2014 44
- 45. ACS Summary • ACS is capable of producing mul-ple Op-mal Execu-on Plans per SQL • During ramp-‐up sub Op-mal Plans may happen • ACS Metadata resides in Memory (not Persistent) • ACS provides desirable Plan Flexibility • ACS does not address the Plan Stability concern Enkitec (c) 2014 45
- 46. SQL Plan Management • 11g+ • Mul-ple Persistent Op-mal Execu-on Plans per SQL • Only “accepted” and “enabled” Plans are Executed • New Plans are acknowledged but not Executed • Goal: Plan Stability with controlled Flexibility Enkitec (c) 2014 46
- 47. SQL Plan Baseline • A set of Plans available to the CBO for a given SQL – Iden-fied by SQL Handle and Signature • Hash func-on on SQL Text • dbms_sqltune.sqltext_to_signature – View dba_sql_plan_baselines • enabled = YES • accepted = YES • reproduced = YES Enkitec (c) 2014 47
- 48. Plan History • Content of dba_sql_plan_baselines • Includes SQL Plan Baseline • Includes Pending Plans – accepted = NO and last_verified is NULL • Includes Rejected Plans – accepted = NO and last_verified is not NULL • Includes Disabled Plans Enkitec (c) 2014 48
- 49. Methods to Create a Plan Baseline 1. Capture 2. Load a. Cursor Cache (CUR) b. SQL Tuning Set (STS) c. Stored Outline 3. Migra-on 1. Capture 2. Load a. b. c. d. e. CUR STS AWR SPA TRC 3. Migra-on Enkitec (c) 2014 49
- 50. Capturing a SQL Plan Baseline (1) • Set op-mizer_use_sql_plan_baselines to TRUE (default) • Set op-mizer_capture_sql_plan_baselines to TRUE (default is FALSE) – Set this parameter at SESSION level • Execute SQL 2 -mes • Set op-mizer_capture_sql_plan_baselines to FALSE Enkitec (c) 2014 50
- 51. Capturing a SQL Plan Baseline (2) Enkitec (c) 2014 51
- 52. Loading SQL Plan Baseline from Cache • dbms_spm.load_plans_from_cursor_cache – Inputs • sql_id • plan_hash_value (opt) – Outputs • Number of Plans loaded Enkitec (c) 2014 52
- 53. Demo 6 • Load Plans for Query out of Demo 5 – demo5.sql – load_plans.sql • Execute Demo 5 again and review Plan History – demo5.sql – list_plans.sql • Execute demo5.sql twice and verify results Enkitec (c) 2014 53
- 54. Demo 6 Results (aoer 1st demo5.sql) CHILD EXECUTIONS BUFFER_GETS PLAN_HASH_VALUE SHAR SENS AWRE -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ 0 3 9090 3022804314 Y Y N CHILD BUCKET_ID COUNT -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ 0 0 0 0 1 1 0 2 2 Note -‐-‐-‐-‐-‐ -‐ SQL plan baseline SQL_PLAN_652hmt7yxthdwd624c0cd used for this statement CREATED PLAN_NAME ENA ACC REP FIX -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdw501f1424 YES YES YES NO 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdwb6c39290 YES YES YES NO 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdwd624c0cd YES YES YES NO 28-‐DEC-‐13 02.03.50.000000 PM SQL_PLAN_652hmt7yxthdwc82a6b0c YES NO YES NO Enkitec (c) 2014 54
- 55. Demo 6 Results (aoer 4rd demo5.sql) CHILD EXECUTIONS BUFFER_GETS PLAN_HASH_VALUE SHAR SENS AWRE -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ 0 2 4274 2163719564 N Y N 1 1 3030 3022804314 Y Y Y 2 1 3030 2326939410 Y Y Y 3 1 1587 2163719564 Y Y Y Note -‐-‐-‐-‐-‐ -‐ SQL plan baseline SQL_PLAN_652hmt7yxthdwb6c39290 used for this statement CREATED PLAN_NAME ENA ACC REP FIX -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdw501f1424 YES YES YES NO 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdwb6c39290 YES YES YES NO 28-‐DEC-‐13 02.03.43.000000 PM SQL_PLAN_652hmt7yxthdwd624c0cd YES YES YES NO 28-‐DEC-‐13 02.03.50.000000 PM SQL_PLAN_652hmt7yxthdwc82a6b0c YES NO YES NO Enkitec (c) 2014 55
- 56. Demo 7 • Drop SQL Plan Baseline – drop_plans.sql • Create SQL Patch with /*+ BIND_AWARE */ Hint – sqlpch.sql connected as SYS • Load Plans for Query out of Demo 5 – demo5.sql – load_plans.sql Enkitec (c) 2014 56
- 57. Demo 7 Results CHILD EXECUTIONS BUFFER_GETS PLAN_HASH_VALUE SHAR SENS AWRE -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ 0 1 3052 2163719564 N Y Y 1 1 3030 2048551027 Y Y Y 2 1 3030 3022804314 Y Y Y 3 1 3030 2326939410 Y Y Y 4 1 1587 2163719564 Y Y Y CREATED PLAN_NAME ENA ACC REP FIX -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ -‐-‐-‐ 28-‐DEC-‐13 02.31.11.000000 PM SQL_PLAN_652hmt7yxthdw501f1424 YES YES YES NO 28-‐DEC-‐13 02.31.11.000000 PM SQL_PLAN_652hmt7yxthdwb6c39290 YES YES YES NO 28-‐DEC-‐13 02.31.11.000000 PM SQL_PLAN_652hmt7yxthdwc82a6b0c YES YES YES NO 28-‐DEC-‐13 02.31.11.000000 PM SQL_PLAN_652hmt7yxthdwd624c0cd YES YES YES NO Enkitec (c) 2014 57
- 58. Demo 8 • Execute queries 1-‐5 and observe how number of Execu-ons increases per Child Cursor – flush.sql – demo8.sql – demo8.sql – demo8.sql Enkitec (c) 2014 58
- 59. Demo 8 Results CHILD EXECUTIONS BUFFER_GETS PLAN_HASH_VALUE SHAR SENS AWRE -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ 0 1 1585 2163719564 N Y Y 1 1 3030 2048551027 Y Y Y 2 1 3030 3022804314 Y Y Y 3 1 3030 2326939410 Y Y Y 4 2 3172 2163719564 Y Y Y Note -‐-‐-‐-‐-‐ -‐ SQL patch "sqlpch_8u0n7w1jug5dg" used for this statement -‐ SQL plan baseline SQL_PLAN_652hmt7yxthdwb6c39290 used for this statement CHILD EXECUTIONS BUFFER_GETS PLAN_HASH_VALUE SHAR SENS AWRE -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ -‐-‐-‐-‐ 0 1 1585 2163719564 N Y Y 1 2 6060 2048551027 Y Y Y 2 2 6060 3022804314 Y Y Y 3 2 6060 2326939410 Y Y Y 4 4 6344 2163719564 Y Y Y Enkitec (c) 2014 59
- 60. Evolving a Plan • Evolving a Plan means “accep-ng” it – Promo-ng it from Plan History into SQL Plan Baseline • dbms_spm.evolve_sql_plan_baseline – sql_handle (opt) – plan_name (opt) – verify (default YES) – commit (default YES) Enkitec (c) 2014 60
- 61. Demo 9 • Drop SQL Plan Baseline – drop_plans.sql • Capture SQL Plan Baseline with 1 accepted Plan – demo9.sql – list_plans.sql • Evolve all Plans on Plan History – evolve.sql Enkitec (c) 2014 61
- 62. FIXED Flag • When set to YES – Only FIXED Plans are considered for Plan Selec-on – No more Plans are Captured into Plan History Enkitec (c) 2014 62
- 63. Plan Selec-on (1) • At hard parse when SQL Plan Baseline (SPB) exists 1. CBO computes an “Op-mal” Plan (OP) • Adap-ve Cursor Sharing is used if applicable 2. If OP exists in SPB then execute this OP 3. If OP does not exist in SPB then store it in Plan History a. If there are FIXED Plans in SPB i. Re-‐cost all FIXED Plans using Binds and execute cheapest b. If there are no FIXED Plans in SPM i. Re-‐cost all Plans using Binds and execute cheapest Enkitec (c) 2014 63
- 64. Plan Selec-on (2) Enkitec (c) 2014 64
- 65. Demo 10 • FIX one Plan from SQL Plan Baseline – alter_plans.sql • Verify only one Plan was Executed – flush.sql – demo8.sql – demo8.sql Enkitec (c) 2014 65
- 66. SPM Summary • SPM provides much desired Plan Stability – Only “approved” Plans are allowed to Execute • ACS can generate a healthy stock of Op-mal Plans – You can restrict them to work under SPM • Combining ACS and SPM you can obtain – Plan Flexibility and Plan Stability Enkitec (c) 2014 66
- 67. SPM/ACS Suggested Strategy • Use dbms_applica-on_info.set_module in your code to set MODULE and ACTION • Use dbms_spm.load_plans_from_cursor_cache filtering with MODULE or ACTION • Use sys.dbms_sqldiag_internal.i_create_patch to SQL Patch with BIND_AWARE the SQL on Baselines • Use dbms_spm.evolve_sql_plan_baseline to verify and evolve periodically good performing Plans Enkitec (c) 2014 67
- 68. Oracle Pack Licenses • DBMS_SPM – No Oracle Pack License • DBMS_SQLTUNE – Oracle Tuning Pack • AWR – Oracle Diagnos-cs Pack Enkitec (c) 2014 68
- 69. References (1) • Random Slowdown by Jonathan Lewis – h{p://jonathanlewis.wordpress.com/2013/12/23/ plan-‐changes/ • Using SQL Patch to add hints to a packaged applica-on – h{ps://blogs.oracle.com/op-mizer/entry/ how_can_i_hint_a Enkitec (c) 2014 69
- 70. References (2) • SQL Plan Management SPM Aware Op-mizer – h{ps://blogs.oracle.com/op-mizer/entry/ sql_plan_management_part_2_of_4_spm_aware_opmizer • SQLTXPLAIN MOS 215187.1 – sqlt/utl/spm Enkitec (c) 2014 70
- 71. References (3) • Oracle® Database PL/SQL Packages and Types Reference – 11g Release 2 (11.2) – Part Number E25788-‐04 Enkitec (c) 2014 71
- 72. Contact Informa-on • carlos.sierra@enkitec.com • carlos-‐sierra.net • @csierra_usa Enkitec (c) 2014 72