How to determine NewSize and Max New Size params for HP JVM.

Answer

Having a large new size would mean that although you have lots of space for creating new objects, you may be trading off the space in the "old heap" (which is where long living objects - like cache etc would live). We have noted that with "default settings", our cache takes up ~ 100-150 MB. So, you would be left with (960 - 125 - 420 = 415MB). In this 415 MB, there would be the 2 survivor spaces where the objects get moved around till they qualify for being classified as "old".

So, one thing we would definitely suggest is to reduce the new size using a "-Xmn of 80M" only (with a ~ 800 MB heap) & Max new size to ~ 80 MB.
We also set the "distributed garbage collection" to kick in every hour, instead of every minute - using the following option: "-Dsun.rmi.dgc.server.gcInterval=3600000" (The time is in milli seconds).

To the best of our knowledge, this is kicked off every minute by some component in WLS to cleanup any distributed objects that may have been created. We have not seen any -ve effects by setting this option.