AFAIK, practically, you can go up to +/-1.5 GB heap per virtual machine on Windows. I found the following a good summary of the story about maximum value for -Xmx and the /3GB switch: http://www.unixville.com/~moazam/categories/jvmInternals/ OTOH, JRockit is said to overcome this limitation by supporting split heaps: http://www.unixville.com/~moazam/categories/jvmInternals/
