How to Fix \"java.lang.OutOfMemoryError: PermGen space\" in Apache Tomcat 6.0?

PermGen Space Exhaustion in Apache Tomcat 6.0

When working with Tomcat 6.0, users may encounter the "java.lang.OutOfMemoryError: PermGen space" error during indexing processes. This issue arises due to insufficient space in the PermGen space, which stores metadata for loaded classes and related information. To resolve this, several solutions can be implemented:

Increasing PermGen Space

The most straightforward method is to increase the maximum PermGen space allocation. This can be achieved by adding the following parameter to the JVM startup script:

<code class="bash">-XX:MaxPermSize=128m</code>

This command sets the maximum PermGen space size to 128 megabytes. However, this approach merely postpones the potential issue rather than eliminating it entirely.

Enabling PermGen Garbage Collection

Alternatively, PermGen garbage collection can be enabled to reclaim unused space. This can be done by adding the following parameters to the JVM startup script:

<code class="bash">-XX:+UseConcMarkSweepGC -XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled</code>

This enables concurrent mark-and-sweep garbage collection for the PermGen space, allowing the JVM to efficiently reclaim unused class metadata and improve performance.

Other Considerations

If the issue persists even after implementing these solutions, the following suggestions can be considered:

• Monitor the PermGen space usage using tools such as VirtualVM or JConsole to verify if the space stabilizes after completing the indexing process.
• Explore migrating to a different JVM, such as the IBM JVM, which does not have a Permanent Generation and is immune to this issue.

By following these guidelines, users can effectively resolve PermGen space exhaustion issues in Tomcat 6.0, ensuring optimal performance during indexing and other related processes.

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