This page last changed on Dec 09, 2007 by mjensen.

I am getting Out of Memory errors, how can I allocate more memory to tomcat?

Since the default memory setting usually is around 64 or 128MB (256MB in Confluence 2.2 and later), you might have to adjust the settings to run a bigger Confluence instance with sufficent memory. Users running Confluence as a service please refer to the Start Confluence automatically on Windows as a Service page. For users running Tomcat standalone, you will have to change the following settings:

Confluence 2.6 with Tomcat 5.5

Do not set your memory using CATALINA_OPTS, because this is overridden by JAVA_OPTS.

On Linux

  • In the unpacked Confluence standalone directory, edit the file bin/setenv.sh
  • Edit the line beginning with JAVA_OPTS= substituting new values for -Xms (starting memory) and -Xmx (maximum memory)
  • Leave the rest of the options in that line unchanged

An example of a minimal setting for a large system - max heap size is set to 1Gb :

JAVA_OPTS="-Xmx1024m $JAVA_OPTS -Djava.awt.headless=true "

On Windows

  • In the unpacked Confluence standalone directory, edit the file bin/setenv.bat
  • Edit the line beginning with set JAVA_OPTS= substituting new values for -Xms (starting memory) and -Xmx (maximum memory)
  • Leave the rest of the options in that line unchanged

Other OutOfMemoryErrors

Other factors such as system load and allocating too much memory to your JVM Heap can also cause OutOfMemory Errors.

OutOfMemoryError: unable to create new native thread

This error occurs when the operating system is unable to create new threads. This is due to the JVM Heap taking up the available RAM.

Big heaps take away from the space that can be allocated for the stack of a new thread

For Linux the maximum heap size of the JVM cannot be greater than 2GB. If you only have 2GB RAM in your server, it is not recommended to set the Max size of the JVM that high.
The size of the stack per thread can also contribute to this problem. The stack size can reduce the number of threads that can be created.

To fix this problem, you should reduce the size of your JVM Heap and also the size of the stack per thread.
The stack size can be changed with the following (example) parameter:

"-Xss512k"

Please refer to this guide as a reference for JVM tuning.

OutOfMemoryError: GC overhead limit exceeded

This error indicates that the JVM took too long to free up memory during its GC process. This error can be thrown from the Parallel or Concurrent collectors.

The parallel collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small. If necessary, this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line.

This kind of OutOfMemoryError can be caused if your java process is starting to use swapped memory for its heap. This will cause the JVM to take a lot longer than normal to perform normal GC operations. This can eventually cause a timeout to occur and cause this error.

To overcome this issue, you need to make sure that all processes can't allocate more memory than there is system memory. In practice this is impossible to do for all processes. At a minimum you should make sure that all your jvm's do not have a total maximum memory allocation than your normally available system memory.

Please refer to this guide for more information.

On OS X

If you are using the 'serveradmin start appserver' to start and stop tomcat, then you will need to update /usr/share/servermgrd/bundles/servermgr_appserver.bundle/Contents/Resources/run.sh

Permanent Generation Size

If you get the error message: java.lang.OutOfMemoryError: PermGen space this means that you have exceeded Java's fixed 64Mb block for loading class files. You will need to add the argument -XX:MaxPermSize=128m to CATALINA_OPTS, in addition to any argument you use to set the heap size.

Please refer to this link for more information.

JDK 1.4 does not provide information why the OutOfMemory error occurred.
JDK 1.5 is recommended as it provides description of the error as in the above example.
JDK 1.6 is not yet officially supported and thus not recommended to use.

RELATED TOPICS

Managing Application Server Memory Settings
Application Server Configuration
FAQ Home
Tomcat JVM options and Modify the Default JVM Settings
Logging A Thread Dump

Document generated by Confluence on Dec 20, 2007 19:02