Websphere performace tuning

HI,

We have deployed my J2EE (includes CMP, Session, MDB beans) application on WAS 6 with oracle as database. Application runs perfectly fine with small dataset but when I point my application to a large recordset (i.e. tables with much more data) it throws OutOfMemory exception. We use IO to read sql queries and other parameters from property files. We also stores data in collection objects at the time of initialization of application.
We have given enough memory for JVM : initial 400 MB, maximum 850 MB. So can anyone give me some performance tuning tips. I have serched on net but its not helping me. Please help me in this. We have also tried various JVM parameters for GC and Heap Size.
please help us in increasing the performance of the system.

Thankx.

Hi Aniket
I suppose the first thing that should be done before an app is deployed to a test environment is to profile the application in the development utility. I'm not sure what the profiling tool is with WAS6 dev tool but with WebSphere Studio there is an IBM agent controller software that can be installed and you can use this to iron out potential performance problems during development. It sounds like you possibly have a memory leak problem. The profiling gives you a set of statistics around method execution time, live instances, details on what objects were collected after GC. I would being profiling your application looking at Class instance stats see what objects are not being collected and the object reference view (where references to objects are being held from other objects).

This is probably where I'd start and you should be able to target your searches on the web around the topics above.

Brian