Documentation for Confluence 3.4.
Documentation for [Confluence Cloud] and the latest Confluence Server is available too.

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Java applications like JIRA and Confluence run in a "Java virtual machine" (JVM), instead of directly within an operating system. When started, the Java virtual machine is allocated a certain amount of memory, which it makes available to applications like JIRA. By default, Java virtual machines are allocated 64Mb of memory, no matter how many gigabytes of memory your server may actually have available. 64Mb is inadequate for medium to large JIRA installations, and so this needs to be increased.

On this page:

Step 1: Diagnosis

 Expand to see diagnosis section

Determine type of error message

Look in the atlassian-confluence.log to see which type of OutOfMemory Error you're receiving. There are three common messages:

  1. Heap Space
  2. Perm Gen Space
  3. GC Overhead

This document discusses increasing memory to address PermGen and Heap space errors. Follow the links above to assess root causes for each issue. For GC Overhead, refer to Confluence crashes due to 'OutOfMemoryError GC overhead limit exceeded' error.

Determine Confluence's usage patterns

In JIRA, go to Administration » System » System Info, and look at the memory graph during times of peak usage:

(info) This server has been allocated a maximum of 650Mb and a minimum of 256m. You can see the minimum displayed here; if you're trying to see whether your settings are being picked up, this is where to look.

Determine available system memory

On Windows

From the Close Programs Dialogue (Press ctrl-alt-delete), select the Performance tab:

(info) The amount marked Available is the amount in kilobytes you have free to allocate to Confluence. On this server we should allocate at most 214Mb.

On Linux

Run cat /proc/meminfo to view the memory usage.

Setting the -Xmx above the available amount on the server runs the risk of OutOfMemoryErrors due to lack of physical memory. If that occurs the system will use swap space, which greatly decreases performance.


The default values supplied with Confluence stand-alone are sufficient for most installations. Please refer to Managing Application Server Memory Settings and Server Hardware Requirements Guide for a discussion.

Step 2: Increase Available Memory


 Expand to see Linux instructions
To increase heap or perm gen space memory in Linux installations,
  1. From <confluence-install>/bin (Stand-alone) or <Tomcat-home>/bin (EAR-WAR installation), open (you can create this file in the EAR/WAR version).
  2. Find the section JAVA_OPTS="-Xms256m -Xmx512m -XX:MaxPermSize=256m ...
  3. See Diagnosis above and enter the appropriate values. Xmx is maximum, Xms is minimum, and MaxPermSize is PermGen.

Windows (starting from .bat file)

 Expand to see Windows .bat file instructions
To Configure System Properties in Windows Installations When Starting from the .bat File,
  1. From <confluence-install>/bin (Stand-alone) or <Tomcat-home>/bin (EAR-WAR installation), open setenv.bat.
  2. Find the section set JAVA_OPTS=%JAVA_OPTS% -Xms256m -Xmx512m -XX:MaxPermSize=256m
  3. See Diagnosis above and enter the appropriate values. Xmx is maximum, Xms is minimum, and MaxPermSize is PermGen.

Windows Service

 Expand to see Windows Service instructions

There are two ways to configure system properties if you Start Confluence Automatically on Windows as a Service - either via command line or in the Windows Registry

Setting Properties for Windows Services via Command Line

Setting Properties for Windows Services via Command Line
  1. Identify the name of the service that Confluence is installed as in Windows ( Control Panel > Administrative Tools > Services ):

    (info) In the above example, the SERVICENAME is: JIRA030908110721
  2. Open the command window from Start >> Run >> type in 'cmd' >> Enter
  3. cd to the bin directory of your Confluence Standalone instance, or the bin directory of your Tomcat installation if your are running Confluence EAR/WAR.
  4. Run:
    tomcat6w //ES//%SERVICENAME%
    (info) In the above example, it would be tomcat6w //ES//JIRA030908110721 (this is a JIRA screenshot, but the same applies to Confluence)
  5. Click on the Java tab to see the list of current start-up options:
  6. Set the maximum memory allocation here

Setting Properties for Windows Services via the Windows Registry

In some versions of Windows, there is no option to add Java variables to the service. In these cases, you must add the properties by viewing the option list in the registry.

To Set Properties for Windows Services via the Windows Registry,
  1. Go to {{Start >> Run, and run "regedit32.exe".
  2. Find the Services entry:
    32-bit: HKEY_LOCAL_MACHINE >> SOFTWARE >> Apache Software Foundation >> Procrun 2.0 >> Confluence
    64-bit: HKEY_LOCAL_MACHINE >> SOFTWARE >> Wow6432Node >> Apache Software Foundation >> Procrun 2.0 >> Confluence
  3. To change existing properties, especially increasing Xmx memory, double-click the appropriate value.
  4. To change additional properties, double-click options.
  5. Modify the memory allocations here.

Step 3: Verify Your Settings

 Expand to see verification instructions

To verify what settings are in place, check Viewing System Information. You should see a section called "Java Runtime Arguments".
(info) Look for Xmx (maximum) and Xms (minimum) settings.
Alternatively, on Linux, run ps -aux | grep java to see the environment parameters.