When it is likely that the RPG app which employs java classes will be
called while servicing a web based request then the overhead of JVM
startup is not necessarily much of an issue where each thread of the
HTTP server persists to service many requests.
For versioning, I set this environment variable at *SYS level
QIBM_RPG_JAVA_PROPERTIES = '-Djava.version=1.4;'
I would suggest that green screen JVM use is horses for courses.
Invoking any trivial class via an INLPGM may not even be noticed by many
users unless they log on and off frequently. A simpler design is always
easier to implement, moving to a background JVM only if necessary.
-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[
mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Walden H. Leverich
Sent: Thursday, 28 June 2007 4:52 a.m.
To: RPG programming on the AS400 / iSeries
Subject: Overhead/downsides to JVM in each job (was: JVM properties -
angst)
In "JVM properties - angst" Peter wrote:
One solution is to launch, or have running, a separate job (and thus a
separate JVM) for each senario. But this means code to communicate
with
and manage those jobs.
Related to that statement, we've recently deployed a java application
that requires Java 5 on the 400 side and while it's available in V5R4,
it doesn't appear to be the default JVM.
We were hoping to just call the java classes we needed from an RPG
program, but we were worried about not knowing if the current JVM was
the 1.5 JVM; if something had already started a java app we'd be in a
1.4 JVM and fail. So we offloaded the java communication to a background
process and dataq-ed the communication back and forth. We also said to
ourselves "well, this saves the overhead of a jvm in each job." But we
said it w/out any good reason.
I know of many installations running JVMs on the System i, but they're
all in the context of a batch process app server (tomcat, websphere,
etc.) For those that are calling java programs from interactive jobs,
what's the performance like? Both from a first call (start JVM) and a
subsequent (active JVM) point of view? Is it something you'd want to do?
-Walden
--
Walden H Leverich III
Tech Software
(516) 627-3800 x3051
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com
Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)
--
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