Session id: The Self-Managing Database: Guided Application and SQL Tuning

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2 Session id: The Self-Managing Database: Guided Application and SQL Tuning

3 Lead Architects Benoit Dageville Khaled Yagoub Mohamed Zait Mohamed Ziauddin

4 Agenda SQL Tuning Challenges Automatic SQL Tuning Overview Usage Scenarios High load SQL tuning Custom SQL workload tuning User Interface Enterprise Manager DBMS_SQLTUNE PL/SQL package Conclusion

5 Manual SQL Tuning Challenges How can I select high-load SQL? How can I tune high-load SQL? SQL Workload DBA High-Load SQL DBA

6 Manual SQL Tuning Challenges Requires expertise in several domains SQL optimization: adjust the execution plan Access design: provide fast data access SQL design: use appropriate SQL constructs Time consuming Each SQL statement is unique Potentially large number of statements to tune Never ending task SQL workload always evolving Plan regressions

7 Packaged App Tuning Scenario Problem: Incorrect Optimizer Mode Selection 1. Get explain plan Manual Tuning 2. Examine query objects and their sizes 3. Review and compare explain plan statistics with execution statistics (stored in V$SQL view) 4. Identify that it is a first rows issue because only recent data is ever displayed despite large history being queried 5. Contact application vendor 6. Produce test case for vendor 7. Get a patch with first rows hint from the vendor 8. Install the patch in next maintenance cycle

8 Oracle 10g SQL Tuning Solution Application & SQL Management Storage Management System Resource Management Database Control Backup & Recovery Management Database Management Intelligent Infrastructure Space Management

9 Oracle 10g Automates the SQL Tuning Process I can do it for you! ADDM High-Load SQL DBA SQL Workload SQL Tuning Advisor

10 Agenda SQL Tuning Challenges Automatic SQL Tuning Overview Usage Scenarios High load SQL tuning Custom SQL workload tuning User Interface Enterprise Manager DBMS_SQLTUNE PL/SQL package Conclusion

11 Automatic SQL Tuning Overview Automatic Tuning Optimizer Statistics Analysis SQL Tuning Advisor SQL Tuning Recommendations Gather Missing or Stale Statistics SQL Profiling Create a SQL Profile Access Path Analysis Add Missing Indexes DBA SQL Structure Analysis Modify SQL Constructs

12 Automatic Tuning Optimizer (ATO) It is the query optimizer running in tuning mode Uses same plan generation process but performs additional steps that require lot more time It performs verification steps To validate statistics and its own estimates Uses dynamic sampling and partial executions to validate It performs exploratory steps To investigate the use of new indexes that could provide significant speed-up To analyze SQL constructs that led to expensive plan operators

13 Statistics Analysis Automatic Tuning Optimizer Statistics Analysis SQL Tuning Advisor SQL Tuning Recommendations Gather Missing or Stale Statistics SQL Profiling Create a SQL Profile Access Path Analysis Add Missing Indexes DBA SQL Structure Analysis Modify SQL Constructs

14 Statistics Analysis Motivation Statistics are key input to the query optimizer Their availability and accuracy is very important In Oracle10g, the Automatic statistics collection maintains statistics up to date But it may not be enabled or properly configured! The ATO verifies statistics that it needs/uses Generates auxiliary information to compensate for missing or stale statistics Generates recommendations to gather statistics where appropriate

15 SQL Profiling Automatic Tuning Optimizer Statistics Analysis SQL Tuning Advisor SQL Tuning Recommendations Gather Missing or Stale Statistics SQL Profiling Create a SQL Profile Access Path Analysis Add Missing Indexes DBA SQL Structure Analysis Modify SQL Constructs

16 SQL Profiling Motivation Empower the query optimizer to find a better plan The query optimizer has time constraints Makes compromises while finding right plan The ATO is allowed a lot more time Uses the time to gather customized information about the SQL statement, known as SQL Profile Builds a SQL Profile and recommends it Once implemented, SQL Profile is used by the query optimizer to generate a well-tuned plan

17 SQL Profiling Flow SQL Profiling SQL Tuning Advisor submit Optimizer (Tuning Mode) create use SQL Profile After Database Users submit Optimizer (Normal Mode) output Well-Tuned Plan

18 SQL Profile It contains auxiliary information collected by the ATO for a SQL statement Customized optimizer settings Based on past execution history (e.g., first_rows vs. all_rows) Compensation for missing or stale statistics Compensation for errors in optimizer estimates Estimation errors occur due to data skews and correlations, complex filters and joins It doesn t require any change to the SQL text Ideal for Packaged Apps It is persistent Works across shutdowns and upgrades

19 Access Path Analysis Automatic Tuning Optimizer Statistics Analysis SQL Tuning Advisor SQL Tuning Recommendations Gather Missing or Stale Statistics SQL Profiling Create a SQL Profile Access Path Analysis Add Missing Indexes DBA SQL Structure Analysis Modify SQL Constructs

20 Access Path Analysis Motivation Adding an index may significantly improve the performance of a SQL statement Problem: A critical access path is missing Index not created or mistakenly dropped ATO explores the use of new indexes Recommends an index if it provides a major performance boost Also recommends to run SQL Access Advisor to get comprehensive index analysis based on a workload SQL Access Advisor also uses this analysis mode

21 SQL Structure Analysis Automatic Tuning Optimizer Statistics Analysis SQL Tuning Advisor SQL Tuning Recommendations Gather Missing or Stale Statistics SQL Profiling Create a SQL Profile Access Path Analysis Add Missing Indexes DBA SQL Structure Analysis Modify SQL Constructs

22 SQL Structure Analysis Motivation Help application developers identify poorly written SQL statements Suggest restructuring of SQL for efficiency Problem categories Semantic changes of SQL operators (e.g., use UNION ALL instead of UNION) Subject to user acceptance of new result Syntactic changes to predicates on indexed columns (e.g., remove type mismatch in column = :bind) SQL design issues (e.g., add missing join predicate to eliminate a large Cartesian join)

23 Agenda SQL Tuning Challenges Automatic SQL Tuning Overview Usage Scenarios High load SQL tuning Custom SQL workload tuning User Interface Enterprise Manager DBMS_SQLTUNE PL/SQL package Conclusion

24 SQL Tuning Usage Scenarios Automatic Selection AWR ADDM High-load SQL SQL Sources Manual Selection AWR Cursor Cache Filter / Rank SQL Tuning Set (STS) SQL Tuning Advisor User-defined

25 SQL Tuning Set (STS) Motivation Enable user to tune a custom set of SQL statements It is a new object in Oracle10g for capturing SQL workload It stores SQL statements along with.. Execution context: parsing user, bind values, etc. Execution statistics: buffer gets, CPU time, elapse time, number of executions, etc. It is created from a SQL source Sources: AWR, cursor cache, user-defined SQL workload, another STS

26 SQL Tuning Set Benefits Allows selective, on-demand, custom SQL workload tuning It simplifies tuning of a large number of SQL statements It is persistent Provides a common infrastructure for dealing with SQL workloads Can be used as a source for different tuning tasks

27 Agenda SQL Tuning Challenges Automatic SQL Tuning Overview Usage Scenarios High load SQL tuning Custom SQL workload tuning User Interface Enterprise Manager DBMS_SQLTUNE PL/SQL package Conclusion

28 Enterprise Manager Interface Launch SQL Tuning Advisor from a SQL Source page ADDM Finding page, or Top SQL page, or SQL Tuning Set (STS) page View SQL Tuning Recommendations Implement SQL Tuning Recommendations

29 SQL Source: ADDM Finding

30 SQL Source: Top SQL

31 SQL Source: SQL Tuning Set

32 SQL Tuning Options

33 Enterprise Manager Interface Launch SQL Tuning Advisor from a SQL Source page ADDM Finding page, or Top SQL page, or SQL Tuning Set (STS) page View SQL Tuning Recommendations Implement SQL Tuning Recommendations

34 SQL Tuning Recommendations Overview

35 SQL Tuning Recommendations Details

36 Enterprise Manager Interface Launch SQL Tuning Advisor from a SQL Source page ADDM Finding page, or Top SQL page, or SQL Tuning Set (STS) page View SQL Tuning Recommendations Implement SQL Tuning Recommendations

37 Implement Recommendations

38 Implement Recommendations

39 Agenda SQL Tuning Challenges Automatic SQL Tuning Overview Usage Scenarios High load SQL tuning Custom SQL workload tuning User Interface Enterprise Manager DBMS_SQLTUNE PL/SQL package Conclusion

40 DBMS_SQLTUNE PL/SQL Package Contains API for SQL Tuning Tuning Task Management Create Tuning Task Execute Tuning Task Display Advisor Recommendations Drop Tuning Task STS Management Create STS Populate STS Query STS Contents Drop STS SQL Profile Management Accept SQL Profile Drop SQL Profile Alter SQL Profile Attribute

41 Conclusion Problem: Incorrect Optimizer Mode Selection Manual Tuning 1. Get explain plan 2. Examine query objects and their sizes 3. Review and compare explain plan statistics with execution statistics (stored in V$SQL view) 4. Identify that it is a first rows issue because only recent data is ever displayed despite large history being queried 5. Contact application vendor 6. Produce test case for vendor 7. Get a patch with first rows hint from the vendor 8. Install the patch in next maintenance cycle Automatic Tuning 1. Run SQL Tuning Advisor 2. Implement SQL profile

42 Recommended Sessions/Demos Technical Sessions Automatic SGA Memory Management (Tuesday, 5 PM, Room 103) The Invisible Oracle: Deploying Oracle DB in Embedded Environments (Wednesday, 4:30 PM, Room 103 Automatic Health Monitoring (Thursday, 11:00 AM, Room 103 Using the Oracle Database 10g SQL Access Advisor (Thursday, 1:00 PM, Room 102) Campground Demos Proactive Performance Management Automatic Memory Management Proactive Space Management Invisible Installation & Deployment Automatic Storage Management Easy Upgrade

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44 Q U E S T I O N S A N S W E R S

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