"the JNI support is buggy (never saw a "crashing" JVM without usage of RPG
JNI calls)"

I've repeatedly seen a JVM invoked in debugging mode have the debugger crash
(causing the whole process to refuse exiting), even with the new JVM on V6R1
(where it was very easy to trigger).

After summer vacation I'll look into finding a reproducible scenario and
bring it up with IBM.

I've also noticed that the IBM documentation is very fond of putting things
in ext. I've wondered why.


-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of D*B
Sent: 29. juni 2012 09:27
To: java400-l@xxxxxxxxxxxx
Subject: RE: RPG, JVM and ClassPath V7R1

... the directory for the Java extension mechanism normaly is
/QIBM/ProdData/Java400/ext and additional /QIBM/UserData/Java400/ext, not
depending on the java version; this is documented in the JDK docu of AS/400
(and all compatible systems). I have found lots of rubbish here in most
installations!!!
I don't use JNI calls from RPG to Java and I don't recommend this, because:
- it's near to impossible to controll the JVM properties (you have maybe one
of the problems)
- the JNI support is buggy (never saw a "crashing" JVM without usage of RPG
JNI calls)
- starting multiple JVMs is not recommended (Performace capabilities
reference V7R1 page 176) I'm using one prestarted JVM serving multiple RPG
clients in a multithreaded environment since about ten years (I have
published this later on as OpenSource Framework AppServer4RPG - BTW: ArdGate
is running on AppServer4RPG with very nice performance and scalability).
So I have none experience with RPG JNI calls of my own.

For further investigation maybe you could do:
- hava look to the ext directories, if there might be an outdated version of
one of your jar files
- superseed the ext mechanism by setting the java property extdirs before
starting the JVM
- start the JVM with -verbose
(I don't know, how to manage last 2 recommendations, as I (nearly) never
used the RPG/JNI stuff)

Dieter Bender
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