RE: Java from RPGLE

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Peter Connell
>
> All java classes must use the JVM to run but where does it run for RPGLE?

Peter, you may also want to ask some of this at the JAVA400-L list.  In any
event, as far as we've been able to determine with both guidance from IBM
and from empirical testing is that (as of V5R2, I believe) a job can have
one and only one JVM.  This pertains to batch or interactive jobs.  Once the
JVM is started for that job, it is persistent FOR THAT JOB.  So while
startup issues are reduced and persistence is supported, scalability becomes
a concern as each job gets its own JVM.

The standard way to design a scalable Java interface is still to create good
old server jobs that read data queues.  Since you can do this from Java just
as easily as anywhere else, the idea is to submit a job to batch and have it
service a queue.  Of course, this brings up other problems such as
congestion and persistence, but them's the tradeoffs today.

What we'd all LIKE to see is the ability to start system-wide named JVMs and
be able to "attach" to one by name frmo any job.  This would allow for the
slickest sort of cross-job communication, but the memory management issues
seem to be beyond the JVM team at this point.

Joe