As customers are beginning to create and deploy huge 64 bit client (GUI)
based applications via Java Webstart (jnlp), the demand for GC tuning on the
client side increases.
Unfortunately there is currently only a very limited set of GC options
available in the list of supported java-vm-args:
http://java.sun.com/javase/6/docs/technotes/guides/javaws/developersguide/syntax.html
Anything not listed is being ignored silently.

It is understood that any option can be used if the application is fully trusted,
which means, also the jnlp file has to be signed. However, many customers create
and customize jnlp files on the fly. So they cannot easily use this approach.

The RFE is to increase the list of supported options starting with the following:

Prio 1:

-XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-XX:+TraceClassUnloading
-XX:+PrintHeapAtGC
-XX:PrintCMSStatistics
-XX:+PrintTenuringDistribution
-XX:SurvivorRatio
-XX:MaxTenuringThreshol
-XX:CMSMarkStackSize
-XX:CMSMarkStackSizeMax
-XX:+UseConcMarkSweepGC
-XX:+CMSClassUnloadingEnabled
-XX:+CMSIncrementalMode
-XX:CMSIncrementalDutyCycleMin
-XX:+CMSIncrementalPacing
-XX:-ParallelRefProcEnabled
-XX:ParallelGCThreads
-XX:ParallelCMSThreads
-XX:+CMSClassUnloadingEnabled
-XX:CMSInitiatingOccupancyFraction
-XX:+DisableExplicitGC
-XX:+UseCompressedOops

Prio 2:
-XX:+UseG1GC
-XX:GCPauseIntervalMillis
-XX:MaxGCPauseMillis
also need :sun.lang.ClassLoader.allowArraySyntax=true
(closing this seperate bug as a dupe)
Also add support for
     -Dsun.lang.ClassLoader.allowArraySyntax=true
(This property is needed to woraround for the bug 6434149 for JAVA 1.6 )

See see also bugs for more details.