I think
you should ask this question - why do you need to do Heap Tuning - are you seeing excessive GC happening - then identify - what GC is happening excessive - Minor one / Major ones.
Is there an issue with the Application - too much object creation etc
Have you tried to answer those questions
Sometimes some 3rd party libraries - call GC explicitly in the code - try to see if you can add this flag
-DisableExplicitGC in the JVM_OPT and see if it reduces the number of GCs