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  1.  Home
  2. JAVA400-L
  3. November 2010

RE: .jar files in use on a restore

I did some poking around and found this reference: http://forums.systeminetwork.com/isnetforums/showthread.php?t=44454

Apparently the only reliable way to end the jvm and clean up all the references as you need it to is RRTJOB.



-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx] On Behalf Of Anna Abt
Sent: Tuesday, November 02, 2010 4:02 PM
To: 'Java Programming on and around the IBM i'
Subject: RE: .jar files in use on a restore

Our software could be run either way. That must be the case, the jvm keeps the lock. I am writing a procedure for install that will monitor for that specific case and install in a temporary folder, notifying the user what happened. I can't think of any other way around it and I can't control what clients are doing.

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx [mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Charles Wilt
Sent: Tuesday, November 02, 2010 4:29 PM
To: Java Programming on and around the IBM i
Subject: Re: .jar files in use on a restore

Are you running interactively?

The JVM in a job doesn't end till the job does. Perhaps the JVM keeps a lock on the .JAR.

Charles

On Tue, Nov 2, 2010 at 3:22 PM, Anna Abt <acosgrove@xxxxxxxxx> wrote:
In order to simplify testing, I asked our java developer to create a
simple
method to call from rpg that made no connections at all to the
iSeries.  I created an rpgle program to call the method.  I have code
that adds a link to the directory, adds the .jar to the environmental
variable, uses getJniEnv and BegObjGroup (jniutil), calls the java
method (defined as a Static Extproc), ends the object group, removes
the environmental
variables
and removes the link.  When I then check the .jar file on the ifs the
usage
is 'in use' under the job that I ran the rpg program in.  I am unable
to restore that object or release it in any way until that session is
signed off.

Having said all that and testing past versions, I've come to the
conclusion
that this was most likely the case for years on installs, we are just
seeing
it more often as the use of java has become more prevalent.  If have
found nothing in my searches as a work around, unless anyone has any ideas.

Thanks

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Tuesday, November 02, 2010 10:36 AM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore

Are you talking about database connections or connections to run
native commands and programs?

JDBC connections use JT400.jar (JTOPEN.jar) and classes from the jre.
I doubt you're replacing any of those. What jars are failing to
replace? Are they your own code?

If you are using the non-thread-safe versions of the connection
commands, those connections occur in jni programs that run within the
same job as
the
jvm. The thread-safe versions are all native java and jdk code
communicating
with server jobs that usually run in the QUSRWRK subsystem. That might
make
a difference when trying to shut down the jvm via the activation group
to free up connections to your jar files.

Just as an afterthought, are you doing anything to your java
environment that would free up hard links before you end the activiation group?

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Tuesday, November 02, 2010 7:33 AM
To: 'Java Programming on and around the IBM i'
Subject: RE: .jar files in use on a restore

The activation group is ended at the end of the rpg processes and also
ended
at the beginning of an install/upgrade.  As this seems to be
intermittent and a fairly new occurrence, I'm leaning toward something
the java code is doing in creating an iSeries connection.  I am
running more tests on our systems to see if I can get more details.


-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Monday, November 01, 2010 6:06 PM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore

As long as that RPG program has pointers to the instantiated object,
you're
not going to be able to replace the jars containing the code for that
object. There are other ways to do it, but you're probably going to
have
to
end the activation group where the RPG program is running in order to
remove
the locks on the jar files. I don't think the traditional methods of
detecting locks are going to find locks on your jar files. WRKOBJLCK,
for instance, looks for objects referenced by the job and a jar file
is not an object. However, the file is "in use".

When RPG uses a java method, RPG invokes the JVM and the JVM "opens"
the
jar
files. The JVM doesn't need the jar file anymore after the class and
object
are instantiated in memory and might close it, except for garbage
collection. The JVM must hold a lock on the jar file as long as it is
running as it might need to read the class from the jar again if
garbage collection has removed the class object when RPG needs to
build a new instance.

Depending on the operating system level, the jvm may run in a separate
job.
In any case it is a unique thread or threads whether in the same job
as
the
RPG or in its own job. All the stuff that connects the RPG to the jvm
is
in
an activation group. If you have the RPG program running in some
activation
group outside the default activation group, the jvm-glue probably runs
in the same activation group. If your RPG program is running in the
default activation group all that glue is probably in its own
activation group. I say probably here, because I'm reporting behavior
as I see it; I don't actually have documentation on this.

So my take on how to do the upgrade you describe would be to have the
CL that runs the RPG program end the activation group that contains
the RPG program; do the jar file replaces; then start the RPG program
back up
again.
This should work in just about all operating systems and versions of java.

Anyone else care to contribute?

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Monday, November 01, 2010 4:07 PM
To: 'Java Programming on and around the IBM i'
Subject: RE: .jar files in use on a restore

There was no OS upgrade or PTF applied on our systems since the
problem started, I do not know about clients.  We run v5r3, v5r4, and
v5r6 here
and
support back to v5r2 for our customer base.   RPG invokes the jvm and
sets the class path and environmental variables and begins and ends
the object group.  RPG calls the methods within an instantiated
object.  Before any upgrades locks on all rpg objects are checked and
the upgrade will not continue if it cannot allocate all objects.  The
basic processing on the
rpg
side has been the same for a number of years.  Some java methods were
connecting to the iSeries for data retrieval.

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dan Kimmel
Sent: Monday, November 01, 2010 4:28 PM
To: Java Programming on and around the IBM i
Subject: RE: .jar files in use on a restore

I think the connection pool is a red herring. The problem probably has
more
to do with an OS upgrade or PTF applied in the last year. I'd need to
know
a
lot more to offer any other suggestions. What OS version? What kind of
programs use the jar files? How is the jvm invoked? Where does the rpg
program enter the picture? Is the rpg program calling methods on
objects
in
the jar files? Do you stop all instances of the rpg program before
attempting to replace the jar files?

-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Anna Abt
Sent: Monday, November 01, 2010 2:38 PM
To: java400-l@xxxxxxxxxxxx
Subject: .jar files in use on a restore

Recently we have run into an issue when trying to run upgrades of our
software.  I have a clle program that does a restore to an ifs
directory with new .jar files.  There have been instances lately where
objects have not been restored because they are in use.  Speaking with
our java programmers I did learn that there was a change made in the
past year to create a connection pool and keep it open for a longer
period of time for performance enhancing reasons.  Doing some testing,
we removed the connection and are now sending the data from the rpg
programs to the java methods.  We are still finding that the .jar files stay in a "in use"
state.
Can anyone tell me how we might get around this or why this seems to
be happening all of a sudden?  We even did a simple test adding a
classpath
of
3 .jar files and running 2 programs, the first opens a connection and
prints
and the second closes the connection.  Those 3 files still are in use
and unable to run a restore against.







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