hello, I hope you can help me on the problem we have with SUSE and JDK 1.4.x: my suse is PAE enabled with 15Gb RAM. unfotunately jvm cannot allocate more than 1900Mb for heap size. So java -Xmx2048m gives me an error. it seems you had the same problem, did you solve it? I hope so :)
thanks Michelangelo
In JDK 1.4 I think you are out of luck. It's a 32-bit JVM, period. You will need to update to a much newer version of Java.
You should be able to use -mx1960m, but not 2GB indeed. You might want to read http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4435069.
Run multiples JVMs to workaround this "limitation" (but, why do you need that much a heap size for?).
Or update to Java 1.5 to reach the theoretical 4GB limit of a 32-bit JVM which can be much lower in practice (see http://forums.sun.com/thread.jspa?threadID=5207549&start=15). But, again, why do you need that much a heap size for?
The JVM is limited to a single contiguous block of memory, so although you might be able to tweak a few more MB out of your system by shutting down processes that you don't really need, the only way to see a big increase is to upgrade to a 64 bit Operating System with a 64 bit JRE.
Update: There's a related question on Stack Overflow with some nice answers: What is the Maximum Java Heap Space for SuSE Linux
just a couple of updates: - on this SUSE machine (where jvm heap max size is 1960m) I can allocate 3.6Gb of heap with several malloc of 10Mb each (C programming). So it sounds quite strange to me. - on another RH4 with same jdk1.4.2 I can allocate: /usr/local/jdks/j2sdk1.4.2_16/bin/java -Xmx2648m with success!! do you know my real RAM on this RH4? just 1024Mb!!! - both SUSE9 and RH4 are PAE enabled (i changed RAM settings easly cause I use VMWare).
So it seems a problem related to SUSE.