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This page covers conditions under which Confluence will become unresponsive and need a restart . It does not cover stack trace error messages thrown from specific uses of Confluence, nor does it cover inability to get Confluence running. Consult Performance Tuning and Garbage Collector Performance Issues if Confluence could be a bit faster or Confluence Startup Problems Troubleshooting if Confluence cannot start.

Gathering Information.

The first thing to do when Confluence freezes or becomes unresponsive (but the Java process is still running) is to take four thread dumps, separated by 30 seconds between each dump. Thread dumps will show what threads are currently running, (what Confluence is currently doing at the moment the thread dump is taken) and will greatly help diagnosing your issue.

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One good tool for analysing a thread dump is TDA.

After taking the thread dumps, raise a support ticket. Remember to include your thread dumps and other logs.

Known causes for crashes

Running in a virtual operating environment

See our note about virtual environments:

Virtual Environments such as VMware may encounter performance problems. These performance issues are especially significant for clustered Confluence.

Java Seg Faults

If Java itself can crash, either due to a bug in Confluence or the JDK. See SIGSEGV Segmentation Fault JVM Crash.

Database Performance

Check Improving Database Performance.

Out of Memory: Permgen space

Search the atlassian-confluence.log file for the text java.lang.OutOfMemoryError: PermGen space. You can solve this problem by increasing your PermGen space to 256M. Make sure to specify PermGen space as opposed to heap space. PermGen space is a straight-forward increase of the memory setting.

Out of Memory: Heap space

Unlike PermGen space, Heap space memory may indicate a memory leak and can require more troubleshooting than just increasing the amount. Managing memory settings requires some analysis; there is no appropriate universal recommendation. To determine if your heap space memory is too low, make sure your XML backup is disabled (see below) and enter plugin safe mode to eliminate memory leak possibilities from our two most likely sources. Once you've done that, read through our suggestions for setting the ideal settings for your environment.

Cluster Panic Messages

Especially in Confluence 3.0.1 or 3.0.2, cluster panics can render the instance inoperable. See 'Database is being updated by an instance which is not part of the current cluster' Error Message.

Plugin related issues

The following plugins have caused suspended threads in some cases. This does not mean these plugins won't work, just that in some cases they may be problematic:

In some cases, these plugins may need upgrading or other maintenance. In some cases they must be disabled. On each plugin's page, you can browse the jira issues. Try entering plugin safe mode for troubleshooting purposes.

Remote API

Remote API scripts can hammer Confluence into submission! If you've recently added a script, remove it for troubleshooting purposes or disable the Remote API.

Databases: SQL Server 2000 and HSQLDB

SQL Server 2000 has been problematic. Use MSSQL 2005 instead. See our Known Issues for SQL Server.
The in-memory database HSQLDB is for evaluation purposes only. Make sure to migrate to a new database when moving into production.

XML Backups

The XML backup is known to be inefficient. With large instances, it can crash the server. Move to the Production Backup Strategy for an efficient and reliable backup solution.

LDAP and Hibernate cache

Verify that the parameter "cache=true" is configured in your <confluence-home>/confluence/WEB-INF/classes/atlassian-user.xml file. It should look like this:

This is a hold-over from CONF-9303.

Search Appliance Indexing

Search robots like Google Search Appliance or others can have a heavy impact on Confluence. Disable these as a test, to understand their impact.

Page Restrictions in Large Spaces

If you have page restrictions in spaces with deep hierarchies, you might hit indexing problems when adjusting the page permissions. See Page Restrictions Performance Considerations.

Upgrade Confluence

There are a variety of upgrades that have been improved through our versions. Make sure to stay current with Confluence versions. The following bugs are known to have caused crashes or hangs:

Upgrade Java Version

Some issues are corrected and others are improved by Java 1.6. Java 1.6 is supported in Confluence 2.7.

Check known performance issues from our Knowledge Base

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