Question

I am running a server with the following attributes:

Windows Server 2008 R2 Standard – 64bit
4gb RAM

I am trying to set the heap size to 3gb for an application. I am using the flags -Xmx3G -Xms3G. Running with the flags results in the following error:

Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

I have been playing with the setting to see what my ceiling is and found that 1568 is my ceiling. What am I missing?

Answer 1

Java requires continuous virtual memory on startup. On windows, 32-bit application run in an 32-bit emulated environment so you don’t get much more continuous memory than you would in a 32-bit OS. c.f. on Solaris you get over 3 GB virtual memory for 32-bit Java.

I suggest you use the 64-bit version of Java as this will make use of all the memory you have. You still need to have free memory but the larger address space doesn’t suffer from fragmentation.

BTW: The heap space is only part of the memory used, you need memory for shared libraries, direct memory, GUI components etc.