Monday Jan 20, 2014

Master Note: Database Performance Overview (Doc ID 402983.1)

Purpose
Questions and Answers
Pro-Active Problem Avoidance and Diagnostic Collection
Performance Information Centres
Troubleshooting Guides
Common Problem Topics
Slow Database Performance
Concurrency Issues
Database Hangs/Spins
Session 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
Performance Diagnostics References
General Diagnostics Overview
AWR/Statspack
10046 Trace
Systemstates/Hanganalyze
Errorstacks for Performance Issues
PStack
PL/SQL Profiler
OS Watcher
LTOM
Trace/Result Interpretation
Performance (and other) Webcasts
Performance and Scalability White Papers and Documentation
Interacting With Performance Support
Community: Database Tuning
References

Applies to:

Oracle Database - Standard Edition - Version 7.0.16.0 and later
Oracle Database - Personal Edition - Version 7.1.4.0 and later
Oracle Database - Enterprise Edition - Version 6.0.0.0 and later
Enterprise Manager for Oracle Database - Version 8.1.7.4 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

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

  • Slow Database Performance

    If the database is performing slowly see the following:

    Document 1362329.1 How To Investigate Slow 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
  • 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 68738.1 No Response from the Server, Does it Hang or Spin?

    Document 392037.1 Database Hangs. Sessions wait for 'resmgr:cpu quantum'
  • Session Hangs/Spins

    If an individual session appears to hang or spin conditions refer to the relevant sections in the following articles:

    Document 1362329.1 How To Investigate Slow Database Performance Issues
    Document 352648.1 How to Diagnose high CPU usage problems
  • 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.

    This webcast can be found here:


    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 1392633.1 Things to Consider before upgrading to 11.2.0.3 to avoid performance or wrong results
    Document 1320966.1 Things to Consider before upgrading to 11.2.0.2 to avoid 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 Upgrade
  • 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 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.
    • 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.

    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

  • 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

  • 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
  • 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
    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 (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



References

NOTE:1320966.1 - Things to Consider Before Upgrading to 11.2.0.2 to Avoid Poor Performance or Wrong Results
NOTE:461228.1 - The LTOM Graph FAQ
NOTE:175006.1 - Steps to generate HANGANALYZE trace files (9i and below)
NOTE:18251.1 - OERR: ORA 60 "deadlock detected while waiting for resource"
NOTE:452358.1 - How to Collect Diagnostics for Database Hanging Issues
NOTE:199083.1 - * Master Note: SQL Query Performance Overview
NOTE:223117.1 - Troubleshooting I/O-related waits
NOTE:68738.1 - No Response from the Server, Does it Hang or Spin?

NOTE:387914.1 - WRH$_ACTIVE_SESSION_HISTORY Does Not Get Purged
NOTE:390374.1 - Oracle Performance Diagnostic Guide (OPDG)
NOTE:392037.1 - Database 'Hangs'. Sessions Wait for 'resmgr:cpu quantum'
NOTE:166650.1 - Working Effectively With Support Best Practices
NOTE:461050.1 - The LTOM Graph (LTOMg) User Guide
NOTE:1357946.1 - Troubleshooting 'library cache: mutex X' waits.
NOTE:352648.1 - How to Diagnose High CPU Usage Problems to the Module Level
NOTE:554831.1 - How to Control the Set of Top SQLs Captured During AWR Snapshot Generation
NOTE:398838.1 - FAQ: SQL Query Performance - Frequently Asked Questions
NOTE:465787.1 - How to: Manage CBO Statistics During an Upgrade from 10g or 9i into 11g
NOTE:376442.1 - * How To Collect 10046 Trace (SQL_TRACE) Diagnostics for Performance Issues
NOTE:39817.1 - Interpreting Raw SQL_TRACE output
NOTE:62365.1 - Troubleshooting "ORA-00060 Deadlock Detected" Errors
NOTE:785351.1 - Oracle 11gR2 Upgrade Companion
NOTE:857576.1 - How to Minimise Waits for 'Log File Sync'
NOTE:94224.1 - FAQ- Statspack Complete Reference
NOTE:70609.1 - How To Display Information About Processes on SUN Solaris
NOTE:977975.1 - Diagnose LTOM Connection Problems
NOTE:1055547.1 - SYSAUX Grows Because Optimizer Stats History is Not Purged
NOTE:34592.1 - WAITEVENT: "log file sync" Reference Note
NOTE:352363.1 - LTOM - The On-Board Monitor User Guide
NOTE:601807.1 - Oracle 11gR1 Upgrade Companion
NOTE:210014.1 - How to Log a Good Performance Service Request
NOTE:1377446.1 - * Troubleshooting Performance Issues
NOTE:243755.1 - Script to produce HTML report with top consumers out of PL/SQL Profiler DBMS_PROFILER data
NOTE:1528847.1 - Troubleshooting: Avoiding and Resolving Database Performance Related Issues After Upgrade
NOTE:1392633.1 - Things to Consider Before Upgrading to 11.2.0.3 to Avoid Poor Performance or Wrong Results
NOTE:466181.1 - Oracle 10g Upgrade Companion
NOTE:1361401.1 - Where to Find Information About Performance Related Features
NOTE:1362329.1 - How To Investigate Slow or Hanging Database Performance Issues
NOTE:1363422.1 - Automatic Workload Repository (AWR) Reports - Start Point
NOTE:1364257.1 - How to Collect Errorstacks for use in Diagnosing Performance Issues.
NOTE:163424.1 - How To Identify a Hot Block Within The Database Buffer Cache.
NOTE:1360119.1 - * FAQ: Database Performance Frequently Asked Questions
NOTE:552880.1 - General Guidelines for SYSAUX Space Issues
NOTE:1278149.1 - Intermittent Long 'log file sync' Waits, LGWR Posting Long Write Times, I/O Portion of Wait Minimal

NOTE:1195363.1 - Database Performance and SQL Tuning Documentation on OTN
NOTE:121779.1 - Taking Systemstate Dumps when You cannot Connect to Oracle
NOTE:62143.1 - Troubleshooting: Tuning the Shared Pool and Tuning Library Cache Latch Contention
NOTE:1415999.1 - Troubleshooting: Virtual Circuit Waits

NOTE:1064487.1 - Script to Collect Log File Sync Diagnostic Information (lfsdiag.sql)
NOTE:438452.1 - Performance Tools Quick Reference Guide
NOTE:438755.1 - High SQL Version Counts - Script to determine reason(s)
NOTE:461052.1 - LTOM System Profiler - Sample Output
NOTE:278316.1 - Troubleshooting: "WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK! "
NOTE:15476.1 - FAQ: Detecting and Resolving Locking Conflicts and Ora-00060 errors
NOTE:1392319.1 - Master Note: Locks, Enqueues and Deadlocks (ORA-00060)
NOTE:155971.1 - Resolving Intense and "Random" Buffer Busy Wait Performance Problems
NOTE:1376916.1 - Troubleshooting: "log file sync" Waits
NOTE:1292724.1 - Suggestions if your SYSAUX Tablespace grows rapidly or too large
NOTE:62354.1 - Waits for 'Enq: Tx - Row Lock Contention' - Wait Scenario Examples
NOTE:1377998.1 - Troubleshooting: Waits for Mutex Type Events
NOTE:1383594.1 - Collaborate with MOS Database Tuning Community Members
NOTE:762540.1 - Consolidated Reference List Of Notes For Migration / Upgrade Service Requests
NOTE:1356828.1 - FAQ: 'cursor: mutex ..' / 'cursor: pin ..' / 'library cache: mutex ..' Type Wait Events
NOTE:1509919.1 - Master Note for Database Error ORA-00060 "deadlock detected while waiting for resource"

NOTE:781198.1 - Diagnostics for Database Performance Issues
NOTE:273646.1 - How to Diagnose High CPU Utilization of ORACLE.EXE in Windows Environment
NOTE:1342917.1 - Troubleshooting 'latch: cache buffers chains' Wait Contention
NOTE:1349387.1 - Troubleshooting 'cursor: pin S wait on X' waits.
NOTE:296377.1 - Troubleshooting: High Version Count Issues
NOTE:301137.1 - OSWatcher Black Box (Includes: [Video])
NOTE:33453.1 - Locking and Referential Integrity

NOTE:34405.1 - WAITEVENT: "buffer busy waits" Reference Note

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