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From "Berneburg, Cris J. - US" <cberneb...@caci.com>
Subject RE: java.lang.OutOfMemoryError: PermGen space
Date Fri, 21 Oct 2016 16:33:33 GMT
Hi Jon

-----Original Message-----
From: Moore, Jon, Vodafone UK [mailto:Jon.Moore@vodafone.com] 
Sent: Thursday, October 20, 2016 6:00 AM
To: users@tomcat.apache.org
Subject: java.lang.OutOfMemoryError: PermGen space

> I have a problem where our customers application server stops
> working intermittently and when we check the Tomcat logs we get the
> message " java.lang.OutOfMemoryError: PermGen space" but the Tomcat
> service is still running, and we have to restart the Tomcat service. I
> am a complete novice when it comes to Tomcat but am expected to
> resolve this issue as this server is part of the Avaya telephony
> solution.
>
> I have 2 questions please.
>
> 1 - What would be causing this.

In my very limited experience it is likely a "memory leak" in your application "hosted" inside
of Tomcat rather than Tomcat itself.  You will need to debug your application.

I went through something very similar starting in July 2016, starting off as a complete newbie.
 See threads relating to "OutOfMemoryError: PermGen space" for the whole sorry affair.  :-)

> 2 - What are the default Java memory settings for Initial memory pool,
> maximum memory pool size and thread stack size when the fields are
> blank when you use the "Configure Tomcat" interface on Windows. I was
> wondering if changing one or more of these settings would help ?

FWIW, I agree with the other folks saying not to alter these settings as the solution to solve
your problem.  If you have a memory leak, increasing the size of the memory will not stop
the leak.

I suggest following a path that was recommended to me.  Start by reading this:

http://markmail.org/message/fcbvwapt6afyndxn

> 1. Find an app that you can't reload without OOME.
> 2. Get a profiler [...]
> 3. Reload you app once.
> 4. Use the profiler to look for instances of WebappClassLoader.
> 5. Look for the one with the started attribute == false.
> 6. Trace the GC roots for this instance.

In the process, I learned how to perform a Java "heap dump" and how to use a memory analyzer.
 FYI, I used Eclipse Memory Analyzer (free) to track things down.  This will be a learning
experience for you too.  ;-)

> We are running Tomcat 6.0.26 on Windows Server 2008 R2 standard and
> JVM version is 1.6.0_20-b02

Thanks for providing those details.  :-)  We had almost the same setup as you, but Win2012
instead of 2008.  FYI, upgrading from Java 6 to 8 did not fix my memory leak.

Good luck, and let us know your progress!

--
Cris Berneburg
CACI Lead Software Engineer


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