The only JVM param that needs to be increased:
* 512 should be pretty big for any purpose

-XX:MaxPermSize=512m

PermGen space this means that you have exceeded Java’s fixed block for loading class files. Permanent Generation Memory, unlike Java heap space, is the memory allocation for the classes themselves as opposed to the objects created. The error occurs when enough classes are invoked.

Very good article about additional parameters: http://java.dzone.com/articles/busting-permgen-myths

-XX:+CMSClassUnloadingEnabled 
-XX:+CMSPermGenSweepingEnabled 
-XX:+UseConcMarkSweepGC

In short: they are just suggestions to garbage collector about how to clean up perm. gen. space. Also, main difference of JRockit is that it doesn’t have perm. gen. space. Perm. generation occurs in Heap memory. Therefore, it’s usually required to increase -Xmx[size]m when switching to JRockit.

• Java