Memory allocation for Java Webstart Application

You can specify the heap size in the j2se tag like this:

    <resources>
    .........
            <j2se version="1.6.0+" href="" initial-heap-size="1024m" max-heap-size="3000m" />
            <j2se version="1.5.0_05" href="" initial-heap-size="1024m" max-heap-size="3000m" />
            <j2se version="1.4.2_04" href="" initial-heap-size="1024m" max-heap-size="3000m" />        
    .........
    </resources>

And specify every jre version you would use.

If you are running a 32-bit Linux, you can only run a 32-bit JVM which is limited to about 4 Gb memory per instance. I believe this is also the case even if you have more visible to the kernel.

If you really, really need a lot of memory in a single JVM you need to go 64-bit.

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EDIT: Java WebStart was not open sourced for OpenJDK so an alternative implementation is used. Try to download and use Sun Java for this instead. It should be enough to download and unzip the JDK, and run bin/javaws foo.jnlp.

Try to set it by using a manual command line parameter. Something like this:

<j2se version="1.6+" java-vm-args="-Xms3072m"/>