Master Note: Database Performance Overview

Master Note: Database Performance Overview

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

• 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'

• 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

• 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:
  
  
  11G Upgrade Best Practices 
  
  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 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

• 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
  Document 781198.1 Required Diagnostics for Database Performance Issues

• 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

• 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

Community Discussions

Still have questions? Use the communities window below to search for similar discussions or start a new discussion on this subject. (Window is the live community not a screenshot)

Click here to open in main browser window

REFERENCES

NOTE:121779.1 - How to Collect 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:163424.1 - How to Identify Hot Blocks Within the Database Buffer Cache that may be Associated with 'latch: cache buffers chains' Wait Contention 
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
NOTE:155971.1 - Resolving Intense and "Random" Buffer Busy Wait Performance Problems
NOTE:1376916.1 - Troubleshooting: 'Log file sync' Waits
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 - 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:1292724.1 - Suggestions if Your SYSAUX Tablespace Grows Rapidly or Too Large 
NOTE:1360119.1 - * FAQ: Database Performance Frequently Asked Questions
NOTE:62354.1 - Waits for 'Enq: TX - ...' Type Events - Transaction (TX) Lock Example Scenarios
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 (Includes: [Video])
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 Based Upon the Retention Policy
NOTE:390374.1 - Oracle Performance Diagnostic Guide (OPDG)
NOTE:465787.1 - How to: Manage CBO Statistics During an Upgrade from 10g or 9i into 11g/12c
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 Reduce Waits on '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:392037.1 - Database 'Hangs'. Sessions Wait for 'resmgr:cpu quantum'
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 - Main Information Sources
NOTE:552880.1 - General Guidelines for SYSAUX Space Issues
NOTE:1364257.1 - How to Collect Errorstacks for use in Diagnosing Performance Issues.
NOTE:1278149.1 - Intermittent Long 'log file sync' Waits on Veritas ODM, LGWR Posting Long Write Times, I/O Portion of Wait Minimal

NOTE:1195363.1 - Database Performance and SQL Tuning Documentation on OTN
NOTE:33453.1 - Locking and Referential Integrity
NOTE:34405.1 - WAITEVENT: "buffer busy waits" Reference Note
NOTE:461228.1 - The LTOM Graph FAQ
NOTE:175006.1 - Steps to generate HANGANALYZE trace files (9i and below)
NOTE:1320966.1 - Things to Consider Before Upgrading to 11.2.0.2 to Avoid Poor Performance or Wrong Results
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:166650.1 - Working Effectively With Oracle 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

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