Running Java on the MF using JCL:

I have this JCL Job Card:

//USER900D JOB (),CLASS=A,MSGLEVEL=(1,1),MSGCLASS=D,NOTIFY=&SYSUID,
//   REGION=0M  <- note the request for memory from the OS

REGION=0M <- means the IBM OS will AutoSize the memory

of the allocated memory MOST will go to the JVM

the JVM then splits the allocated memory into "sections"

these sections include:
where to load the classes
where to allocate Heap
where to allocat Stack 
(and more)

I can control these allocations via Java command line options

Parameters affecting the memory available to the JVM include:

-Xms: Sets the minimum and initial size of the heap.
-Xmx: Sets the maximum size of the heap.
-XX:PermSize: Sets the initial size of the Permanent Generation (perm) memory area. This option was available prior to JDK 8 but is no longer supported.
-XX:MaxPermSize: Sets the maximum size of the perm memory area. This option was available prior to JDK 8 but is no longer supported.
-XX:MetaspaceSize: Sets the initial size of Metaspace. This option is available starting in JDK 8.
-XX:MaxMetaspaceSize: Sets the maximum size of Metaspace. This option is available starting in JDK 8.


in my JCL I can code:

//JAVA EXEC PGM=BPXBATSL,
// PARM='PGM /usr/lpp/java/J8.0/bin/java -Xms<???>


WARNING: IBM offer both 32 bit and 64 bit Java installions, your need to check
         you are using the 64 bit Java to access lots of memory
         
//JAVA EXEC PGM=BPXBATSL,
// PARM='PGM /usr/lpp/java/J8.0-64/bin/java -Xms<???>