Help!! Can not increase max_heap_size to 2048m

Question

Hi,
I need to increase the max-heap-size parameter of my jnlp file to 2048m. The users absolutely need this as they get out of memory error with the current setup (1024m). But very strange thing happens.
When I change the heap size, and try to launch the JNLP file, it just dies. It does not throw any error message. The system where I tried this, had 8 gm physical memory. So, lack of memory is not an issue.
I will appreciate any help!! We need this resolved ASAP.
Here is how I set it up:
<j2se version="1.4+" max-heap-size="2048m"/>
Thanks~

Answer 1

This is not a Java restriction. Java requests a contiguous area of memory for the heap. Depending on the os, and on what was previously loaded into memory, the value provided by the os can be as small as 1.2 Gb (approx).
Start with the heap value that works, and increase it in increments until it fails. That'll be the limit for that particular machine/setup. An easy way of finding the limit is to use the command
java -Xmx<size> <someClassName>
If the value is too large, you'll get a response like this:
java -Xmx1600m HelloWorldApp
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.