Maximum Heap Size For A Weblogic Server Process Running on a 64-bit JVM [ID 846267.1]
64-bit platforms are not physically limited by the pointer size, and the process size can grow to the supported limit. The limit is therefore equal to the amount of memory installed.
64-bit platforms are not physically limited by the pointer size and the process size can grow to the supported limit. The limit is usually the amount of memory installed, but there can be further limitations imposed by the operating system version (different releases support different amounts, for example Windows 2003/Itanium only supports 16 GB, unless you’re running the EE variant).
Versions of BEA JRockit up to and including 1.4.2 (24.5.0) have a pointerset for the heap that uses a 32-bit index; therefore a heap larger than 24GB will crash the JVM.
You should experience similar performance between releases assuming the hardware you run upon has enough memory installed (which means enough for both the Java process and the operating system).