Here's a good read:
Hints and Tips for Java on z/OS
http://www-03.ibm.com/systems/z/os/zos/tools/java/faq/javafaq.html
Note how if you're using 64 bit java, the ulimit -a command should show that you have memory above the bar available for use:
/u/odv733>ulimit -a
core file unlimited
cpu time unlimited
data size unlimited
file size unlimited
stack size unlimited
file descriptors 64000
address space 1009192k
memory above bar 2048m <-----------
/u/odv733>
Ed
Run the following job on z/OS:
//STEP31 EXEC PGM=BPXBATCH,REGION=0M
//STDPARM DD *
SH ulimit -a
//SYSPRINT DD SYSOUT=*
//STDERR DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SYSPRINT DD SYSOUT=*
//STDERR DD SYSOUT=*
//STDOUT DD SYSOUT=*
//STDENV DD *
_CEE_RUNOPTS=RPTSTG(ON)
/*
//STEP64 EXEC PGM=BPXBATCH
//STDPARM DD *
SH /usr/lpp/java/J7.0_64/bin/java -fullversion
//* Previous line must be a 64 bit version of java for this demo
//SYSPRINT DD SYSOUT=*
//STDERR DD SYSOUT=*
//SYSOUT DD SYSOUT=*
//SYSPRINT DD SYSOUT=*
//STDERR DD SYSOUT=*
//STDOUT DD SYSOUT=*
//STDENV DD *
_CEE_RUNOPTS=RPTSTG(ON)
/*
Okay, maybe I amuse easily, but I find it interesting to see that LE is allocating memory in the second step out in 64-bit land.
If you're on 8.5 of CMOD or above, you should be using 64 bit java.
Ed