WebSphere Java Heap Configuration

Cross-Posted on Web400; Midrange-l

I have a customer running WebSphere 6.1 on an IBM i hosts V6R1. Currently
this implementation is being tested as part of a performance evaluation
process as the application back end database is run on the same IBM i. We
are running WAS with its own dedicated pool of memory.

One of the things we have looked at is how to increase the memory size (if
possible) for the WebSphere Server instance. We currently have this
configured with an initial heap size of 0 and a maximum heap size of 1380
and it runs quite OK. We are running a 32 bit JVM at this point in time but
may move to the 64 bit JVM to see what results that provides

According to the documentation I have read, setting the Initial Heap size
to 96 and Maximum Heap Size to 0 should cause the maximum heap size to be
effectively "nomax". (setting the hap sizes to the same value is not
recommended). However setting the heap sizes this was basically causes the
server to start doing heap dumps and fail.

What do others do to maximise the amount of memory available to the
.application being run by WebSphere ? Has anyone got the recommended
settings to work or some other variation ?

Any advice appreciated.