Oracle Oracle Performance Tuning

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In this Document Purpose Questions and Answers Pro Active Problem Avoidance and Diagnostic Collection Performance Information Centres Troubleshooting Guides Common Problem Topics Commonly searched performance related Events, Warnings and Errors Slow Database Performance Concurrency Issues Hangs Database Hangs/Spins Session Hangs/Spins Single SQL Statement Hangs/Spins

Locking Issues Deadlock Pre Upgrade Planning Post Upgrade Performance Issue Resolution Debugging Waits for Various Events Library Cache/Mutex Contention/Cursor Type Events: Other Types: Common Causes of Performance issues Cursor Sharing/High Version Counts for Cursors High CPU usage Issues With waits for 'log file sync' WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK! Buffer Busy/Cache Buffers Chains Latch waits SYSAUX Issues

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In this Document Performance Diagnostics References Performance Service Request Diagnostic Collection (SRDC) documents General Diagnostics Overview AWR/Statspack 10046 Trace Systemstates/Hanganalyze Errorstacks for Performance Issues PStack PL/SQL Profiler OS Watcher LTOM 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 2/12 Trace/Result Interpretation Performance (and other) Webcasts Performance and Scalability White Papers and Documentation Interacting With Performance Support Community: Database Tuning Community Discussions References



APPLIES TO Oracle Database Enterprise Edition Version 6.0.0.0 and later Oracle Database Personal Edition Version 7.1.4.0 and later Enterprise Manager for Oracle Database Version 8.1.7.4 and later Oracle Database Standard Edition Version 7.0.16.0 and later Information in this document applies to any platform.



PURPOSE This Document provides an overview reference to content that pertains to the resolution of Performance issues affecting the whole database. For the Database Performance Frequently Asked Questions FAQ,information regarding Performance Related Features or issues involving individual SQL statements, see: Document 1360119.1 FAQ: Database Performance Frequently Asked Questions Document 1361401.1 Where to Find Information About Performance Related Features Document 199083.1 Master Note: SQL Query Performance Overview Document 1516494.2 Information Center: SQL Query Performance Overview Document 398838.1 FAQ: SQL Query Performance Frequently Asked Questions



QUESTIONS AND ANSWERS Pro Active Problem Avoidance and Diagnostic Collection Although some problems may be unforeseen, in many cases problems may be avoidable if signs are detected early enough. Additionally, if an issue does occur, it is no use collecting information about that issue after the event. For information on suggested preparations to avoid issues and in case diagnostics are required, see: Document 1482811.1 Best Practices: Proactively Avoiding Database and Query Performance Issues Document 1477599.1 Best Practices Around Data Collection For Performance Issues Performance Information Centres Performance Information Centres provide access to various aspects of performance issues: Document 1512292.2 Information Center: Database Performance Overview Document 1516494.2 Information Center: SQL Query Performance Overview 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 3/12 Troubleshooting Guides There are a number of troubleshooting guides that can help resolve various issues: Document 1543445.2 Troubleshooting Assistant: Troubleshooting Performance Issues Document 1542678.2 Troubleshooting Assistant: SQL Performance Issues Document 1528847.1 Troubleshooting: Avoiding and Resolving Database Performance Related Issues After Upgrade Document 60.1 Troubleshooting Assistant: Oracle Database ORA 00060 Errors on Single Instance (Non RAC) Diagnosing Using Deadlock Graphs in ORA 00060 Trace Files



COMMON PROBLEM TOPICS Commonly searched performance related Events, Warnings and Errors The following lists commonly searched Events, Warnings and Errors that are related to performance and points to key troubleshooting documents: Document 2008188.1 Commonly Searched for Database Performance Related Events, Warnings and Errors Slow Database Performance If the database is performing slowly see the following: Document 1362329.1 How To Investigate Slow or Hanging Database Performance Issues Concurrency Issues If you have problems with the concurrency of transactions, initially treat this as a "Slow Database Performance" issue and refer to the following: Document 1362329.1 How To Investigate Slow Database Performance Issues Hangs Database Hangs/Spins If the database encounters what looks like a hang or a spin conditions refer to the following: Document 452358.1 How to Collect Diagnostics for Database Hanging Issues Document 1362329.1 How To Investigate Slow or Hanging Database Performance Issues Document 68738.1 No Response from the Server, Does it Hang or Spin? Document 392037.1 Database Hangs. Sessions wait for 'resmgr:cpu quantum'



COMMON PROBLEM TOPICS Session Hangs/Spins If an individual session appears to hang or spin refer to the relevant sections in the following articles: Document 1362329.1 How To Investigate Slow or Hanging Database Performance Issues Document 352648.1 How to Diagnose high CPU usage problems Single SQL Statement Hangs/Spins If an individual SQL statement appears to hang or spin refer to the relevant sections in the following articles: Document 1362329.1 How To Investigate Slow or Hanging Database Performance Issues Document 1916479.1 How to Investigate Hanging SQL Statements



COMMON PROBLEM TOPICS Locking Issues If sessions encounter locking conflicts refer to the following: Document 1392319.1 Master Note: Locks, Enqueues and Deadlocks Document 15476.1 FAQ about Detecting and Resolving Locking Conflicts Document 62354.1 TX Transaction locks Example wait scenarios Document 33453.1 REFERENTIAL INTEGRITY AND LOCKING Deadlock ORA 60 is an application error which usually occurs because a consistent locking strategy has not been followed throughout an application. Please refer to the following articles for more information: Document 1509919.1 Master Note for Database Error ORA 00060 Document 18251.1 OERR: ORA 60 "deadlock detected while waiting for resource" Document 62365.1 What to do with "ORA 60 Deadlock Detected" Errors Please ensure that you are encountering none of the conditions in these articles. Pre Upgrade Planning For upgrades to 11g, there is a useful webcast entitled "11G Upgrade Best Practices" : This recorded seminar provides an overview of tips and best practices for upgrading your database to 11G. It starts with general Challenges and Support Best Practices, but moves on to performance specifics such as AWR and STATSPACK, SQL Plan Management, and Real Application Testing.



COMMON PROBLEM TOPICS This webcast can be found here: 11G Upgrade Best Practices 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 5/12 For advice on planning your upgrade see: Document 785351.1 Oracle 11gR2 Upgrade Companion Document 601807.1 Oracle 11gR1 Upgrade Companion Document 466181.1 10g Upgrade Companion Document 465787.1 Managing CBO Stats during an upgrade to 10g or 11g For more general upgrade related information see: Document 1645862.1 Things to Consider Before Upgrading to 11.2.0.4 to Avoid Poor Performance or Wrong Results Document 1392633.1 Things to Consider before Upgrading to 11.2.0.3 to Avoid Poor Performance or Wrong Results Document 1320966.1 Things to Consider before Upgrading to 11.2.0.2 to Avoid Poor Performance or Wrong Results Document 1464274.1 Master Note for Real Application Testing Option Document 762540.1 Consolidated Reference List Of Notes For Migration / Upgrade Service Requests Post Upgrade Performance Issue Resolution To troubleshoot performance issues encountered after upgrading a database see: Document 1528847.1 Troubleshooting: Avoiding and Resolving Database Performance Related Issues After



COMMON PROBLEM TOPICS Debugging Waits for Various Events There are numerous articles to help you debug issues with wait event contention. The most common of these being: Library Cache/Mutex Contention/Cursor Type Events: Document 1356828.1 FAQ: 'cursor: mutex ..' / 'cursor: pin ..' / 'library cache: mutex ..' Type Wait Events Document 1377998.1 Troubleshooting: Waits for Mutex Type Events Document 1349387.1 Troubleshooting 'cursor: pin S wait on X' waits Document 1357946.1 Troubleshooting 'library cache: mutex X' waits. Other Types: Document 1376916.1 Troubleshooting: "Log File Sync" Waits Document 1342917.1 Troubleshooting 'latch: cache buffers chains' Wait Contention Document 34405.1 WAITEVENT: "buffer busy waits" Reference Note Document 223117.1 Troubleshooting I/O related waits Document 1415999.1 Troubleshooting: Virtual Circuit Waits



COMMON PROBLEM TOPICS Common Causes of Performance issues Cursor Sharing/High Version Counts for Cursors The failure to share cursors effectively can have a highly detrimental affect on a database. For example, having hundreds of versions of the same cursor is likely to be wasting space, is unlikely to promote good performance and, in extreme cases, can cause contention issues. For issues linked to Cursor related waits see: Document 1356828.1 FAQ: 'cursor: mutex ..' / 'cursor: pin ..' / 'library cache: mutex ..' Type Wait Events Also, see the following articles for more information and help with troubleshooting issues: Document 296377.1Troubleshooting: High Version Count Issues Document 438755.1 High SQL Version Counts Script to determine reason(s) Document 62143.1 Understanding and Tuning the Shared Pool High CPU usage In cases where CPU usage of individual sessions or the whole database is high, refer to the following: Document 352648.1 How to Diagnose High CPU Usage Problems to the Module Level Document 273646.1 How to diagnose the high CPU utilization of ORACLE.EXE in Windows environment Note that High CPU usage can be caused by many factors including contention for cursors (see above), inefficient SQL and may be associated with excessive buffer reads etc.



COMMON PROBLEM TOPICS Issues With waits for 'log file sync' If your system is waiting for the redo log files to synchronise with the disk, the following articles can help: Document 1376916.1 Troubleshooting: "Log File Sync" Waits Document 34592.1 WAITEVENT: "log file sync" Reference Note Document 857576.1 How to Minimise Waits for 'Log File Sync'? Document 1278149.1 High Log File Sync Wait Events, LGWR Posting Slow Write Times, Low IO Waits Document 1064487.1 Script to Collect Log File Sync Diagnostic Information (lfsdiag.sql) WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK! This Issue occurs when the database detects that a waiter has waited for a resource for longer than a particular threshold. The message "WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK!" appears in the alert log and trace and systemstates are dumped. 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 7/12 Typically this is caused by two (or more) incompatible operations being run simltaneously. See: Document 278316.1 Troubleshooting: "WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK!" Buffer Busy/Cache Buffers Chains Latch waits Buffer Busy waits occur when a session wants to access a database block in the buffer cache but it cannot as the buffer is "busy". Cache Buffers Chains Latch waits are caused by contention where multiple sessions waiting to read the same block. Typical solutions are to look for SQL that accesses the blocks in question and determine if the repeated reads are necessary. Document 1342917.1 Troubleshooting 'latch: cache buffers chains' Wait Contention Document 34405.1 WAITEVENT: "buffer busy waits" Reference Note Document 155971.1 Resolving Intense and "Random" Buffer Busy Wait Performance Problems: Document 163424.1 How To Identify a Hot Block Within The Database Buffer Cache



COMMON PROBLEM TOPICS SYSAUX Issues SYSAUX is a mandatory tablespace in 10g which stores all auxiliary database metadata related to various product options and features. Of particular interest to Performance is the storage of Automatic Workload Repository (AWR) data: Document 552880.1 General Guidelines for SYSAUX Space Issues Document 1055547.1 SYSAUX Grows Because Optimizer Stats History is Not Purged Document 387914.1 WRH$_ACTIVE_SESSION_HISTORY Does Not Get Purged Document 554831.1 How to Control the Set of Top SQLs Captured During AWR Snapshot Generation Document 1292724.1 SYSAUX Tablespace Grows Rapidly



Performance Diagnostics References Performance Service Request Diagnostic Collection (SRDC) documents Service Request Data Collection (SRDC) documents have been specially designed to provide the reader with the necessary instructions to provide a step by step guide to collecting information for a various common Database Performance Issues. Document 1938786.1 List of Available Database Performance Related SRDC Documents General Diagnostics Overview Document 438452.1 Performance Tools Quick Reference Guide 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 8/12 Document 781198.1 Required Diagnostics for Database Performance Issues



Performance Diagnostics References AWR/Statspack Document 1363422.1 AWR Reports Start Point Document 94224.1 FAQ Statspack Complete Reference 10046 Trace Document 376442.1 Recommended Method for Obtaining 10046 trace for Tuning Systemstates/Hanganalyze Document 121779.1 Taking a SYSTEMSTATE dump when you cannot CONNECT to Oracle. Document 175006.1 Steps to generate HANGANALYZE trace files Errorstacks for Performance Issues Document 1364257.1 How to Collect Errorstacks for use in Diagnosing Performance Issues PStack Document 70609.1 How To Display Information About Processes on SUN Solaris



Performance Diagnostics References PL/SQL Profiler Document 243755.1 Implementing and Using the PL/SQL Profiler OS Watcher OS Watcher (OSW) is a collection of UNIX shell scripts intended to collect and archive operating system and network metrics to aid support in diagnosing performance issues. Document 301137.1 OS Watcher User Guide LTOM The Lite Onboard Monitor (LTOM) is a java program designed as a proactive, real time diagnostic platform and provides real time automatic problem detection and data collection. Document 352363.1 LTOM The On Board Monitor User Guide 7/29/2015 Document 402983.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_201&id=402983.1 9/12 Document 461050.1 The LTOM Graph (LTOMg) User Guide Document 461228.1 The LTOM Graph FAQ Document 461052.1 LTOM System Profiler Sample Output Document 977975.1 Diagnose LTOM Connection Problems Trace/Result Interpretation The following articles can help with the interpretation of various diagnostics: Document 390374.1 Oracle Performance Diagnostic Guide (OPDG) Document 39817.1 Interpreting Raw SQL_TRACE and DBMS_SUPPORT.START_TRACE output http://www.oracle.com/technetwork/database/focus areas/performance/statspack opm4 134117.pdf



Performance Diagnostics References Performance (and other) Webcasts A series of Performance (and General Datbase topic) related webcasts, including topics such as SQLHC, SQLTXPLAIN and OSWBB, can be found here: Document 1456176.1 Oracle Database Advisor Webcast Archives Performance and Scalability White Papers and Documentation Performance and Scalability White Papers: http://www.oracle.com/technetwork/database/focus areas/performance/index.html For White papers concerning Real Application Testing (RAT) and SQL Performance Analyzer (SPA) see: Document 1546337.1 Real Application Testing (RAT): Recommended White Papers Links to the main Tuning and Performance documentation: Document 1195363.1 Database Performance and SQL Tuning Documentation on OTN Interacting With Performance Support Document 210014.1 How to Log a Good Performance Service Request Document 166650.1 Working Effectively With Global Customer Support Community: Database Tuning A community has been set up for My Oracle Support (MOS) users moderated by Oracle. The goal of this community is to exchange database related Tuning knowledge and concepts. The community can be found via the following article: Document 1383594.1 Collaborate With MOS Database Tuning Community Members



Performance Tools Quick Reference Guide



ContentsIntroduction Query Tuning Enterprise Manager (SQL Tuning Advisor) AWR SQL Report SQLTXPLAIN TRCANLZR PL/SQ_ Profiler LTOM (Session Trace Collector) OPDG OS Data OS_Watcher Database Tuning Enterprise Manager ADDM ADDM Report STATSPACK AWR Report OPDG Hang, Locking, and Transient Issues ASH Report LTOM (Hang Detector, Data Recorder) HangFG Error/Crash Issues Stackx ORA 600/ORA 7445 Troubleshooter RAC RDA



Introduction The purpose of this note is to provide a quick guide to available tools that can be used for resolving performance issue. A brief description and a link to a more detailed document for 7/29/2015 Document 438452.1 https://support.oracle.com/epmos/faces/DocumentDisplay?_adf.ctrl state=xpn86qnwb_250&id=438452.1 2/7 each available tool is provided below. NOTE: Most of the tools referenced in this note can be installed and used at the time of the performance issue. There are some exceptions however. LTOM and OS Watcher need to be installed and running prior to the performance. More details on these tools are provided below.



Query Tuning A query tuning issue can manifest itself as: A particular SQL statement or group of statements that run slowly at a time when other statements run well. One or more sessions are running slowly and most of the delay occurs during the execution of a particular SQL statement. There are many tools that are beneficial for tuning queries. Use one or more of the below tools when troubleshooting query tuning issues.



Query Tuning



Hang, Locking, and Transient Issues A "true" database hang can manifest itself several ways. Some examples are: A database that is no longer allowing users to connect. A database that is no longer performing work. "Select 1 from dual" does not produce output. Create table does not complete. One or more sessions that have completely stopped functioning is usually identified as a locking issue. Transient issues related to performance are issues that generally occur for a time and then disappear but, during the occurrence, the system is hung or very slow. LTOM and HangFG are tools that assist in collecting the appropriate data when these issues occur. Use these helpful tools and utilities when troubleshooting hang, locking, and transient issues



Hang, Locking, and Transient Issues



Error/Crash Issues In this section, error and crash issues refer to ORA 600, ORA 7445 errors, and core dumps. Use the tools below to assist in troubleshooting these types of issues.



RACUse the RDA tool to obtain helpful performance related data across a RAC cluster.



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