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Former Member

SAP NW 2004S J2EE installation on iSeries v5r4


I need to install the SAP WebAS Java on a new memory pool on iSeries.

SAP Note 717376 states following:

server processes:
initial heapsize (-Xms): 1024M
maximum heapsize (-Xmx): 4096M
dispatcher processes:
initial heapsize (-Xms): (64 * number of J2EE servers)M
maximum heapsize (-Xmx): 2048M (at least 4 * initial size)
bootstrap processes, SDM:
initial heapsize (-Xms): 64M (or don't set it at all)
maximum heapsize (-Xmx): 2048M (or same as Xmx of related Java process)

How do you calculate the size of the memory pool?

Is that the sum of every maximum heapsize?

Best regards,

Nicolas De Corte

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    Former Member
    Sep 17, 2008 at 03:10 PM

    Hi Nicolas,

    with the Classic VM on IBM i this is not just a simple adding equation. Sure, to be on the safe side, it would be nice if you have a memory pool with the size of Xmx (Max Heap Size) of the server process(es), dispatcher and SDM.

    However, in the daily use you have to see where the actual (average) heap consumption of the java processes lies. When you've found that out you can probably add the actual heap sizes of all the processes plus some safety factor of .5 or so.

    It is important to watch out for paging in your Java system's memory pool. If paging occurs you'd better increase the pool.

    Best regards


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