Garbage Collection - GC Policy clarification - Websphere

This is a discussion on Garbage Collection - GC Policy clarification - Websphere ; All I'm having some OOM problems in a a 4 node Portal cluster. A couple of the portlets are handling large objects ( content ) and the heap is expanding due to allocation failures. Eventually, this causes an OutOfMemory error, ...

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Thread: Garbage Collection - GC Policy clarification

  1. Garbage Collection - GC Policy clarification

    All

    I'm having some OOM problems in a a 4 node Portal cluster. A couple of the portlets are handling large objects ( content ) and the heap is expanding due to allocation failures. Eventually, this causes an OutOfMemory error, heapdumps and the portal instance becomes unresponsive until the server is restarted.

    The suspect applications are being analyzed, and I've tuned the JVM to better handle large objects, which has been relatively successful.

    However, the portals are not required to be available 24/7. As they are not used overnight, there are no objects allocated to the heap, no allocation failures and therefore garbage collection doesn't run. Makes sense.

    Is there another GC policy I can use to make use of this downtime to have GC run to reclaim objects from the heap overnight ?

    Thanks in advance.

  2. Re: Garbage Collection - GC Policy clarification

    Hello,
    For WP 6.1 (uses Java 5.0), the GC policies are described in *Frequently asked questions about the Garbage Collector* at http://publib.boulder.ibm.com/infoce...ng/mm_faq.html. This WP version installs with -Xgcpolicy:gencon.

    For WP 6.0 (uses Java 1.4.2), the GC policies are described in *Frequently asked questions about the Garbage Collector* at http://publib.boulder.ibm.com/infoce...questions.html. This WP version installs with the default GC policy (optthruput).

    You can try testing with *-Xgcpolicyptavgpause*. However, if the OOM problem is occurring because the Java heap is exhausted, then that will still happen no matter which GC policy you use.

    Before you test, be sure to install the latest Java SDK cumulative fix available at *Recommended fixes for WebSphere Application Server* at http://www.ibm.com/support/docview.w...id=swg27004980.

    Thank you,
    David Yang
    WebSphere Portal support

    The postings on this site are my own and do not necessarily represent the positions, strategies, or opinions of IBM.

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