java jvm memory assignment

Question

I have a program that is very memory consuming and thought to assign more maximum memory to the java jvm using -Xmx2048m. But when starting I get a 'Could not reserve enough space for object heap' error.

When trying several values and found out that my greatest value is -Xmx1560m and it starts. But I like to assign 2GB. I have 6GB physical Memory and Taskmanager shows 3400MB available after I started the java-process with -Xmx1560m.

Do anyone know why I can't assign 2GB ?

Answer 1

32-bit windows limits programs to around 1.2 - 1.5 GB of continuous memory. This limit applies even if you have a 64-bit OS but you are emulating a 32-bit environment for a 32-bit JVM.

The way to avoid this limit is to use a 64-bit OS and a 64-bit JVM and the limit is much higher depending on the flavour of Windows you have bought. Professional edition is limited to 192 GB.