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From André Warnier (tomcat) ...@ice-sa.com>
Subject Re: java.lang.OutOfMemoryError: PermGen space
Date Fri, 21 Oct 2016 08:33:55 GMT
On 21.10.2016 09:46, Moore, Jon, Vodafone UK wrote:
> Thanks Chris. (and to everyone else who has replied)
>
> Yes I am a novice at Java as well. I support the IVR system that points to the application
servers and have ended up trying to resolve this issue as our developers of the applications
can't help.
>
> The way we are told on the training to deploy the application in the IVR is to use the
deploy/un-deploy options in tomcat manager. I have also seen a colleague make a copy of the
applications war file away from its normal folder (webapps), stop the tomcat Windows service,
delete the applications deployed folder and restart the tomcat windows service to re-deploy
the application.
>
> I have tried to run the commands you suggested from a CMD box but nothing gets outputted.
>

Some additional info :

When Tomcat is running as a Service under Windows, the Java command-line switches (which 
allow to control the Java memory sizes among other tings), are stored in the Windows 
Registry.  The Windows Tomcat-as-a-Service installation includes a program (named 
"tomcat(version)w.exe", which is a kind of GUI Registry Editor, specially for these 
Java/Tomcat related parameters.  Normally, this program is running, and appears as a small

Apache icon at the bottom right of the console.
That is the program that you should use, to change the Java startup parameters, and 
stop/start Tomcat.

As explained in previous posts here on this list, and in some of the articles to which I 
pointed you in Google, it may be that your issue is only that the default PermGen size, is

insufficient for your application(s), and that just increasing the Java PermGen size would

solve the problem definitely.

Or not, if the application is flawed. But you can at least try.

For the full story about tomcat(x)w.exe, try the Tomcat FAQ (which does not seem to be 
on-line right now, or very slow), and look for an article entitled "what are tomcatx.exe 
and tomcatxw.exe".
Ah, here : http://wiki.apache.org/tomcat/FAQ/Windows


>
> -----Original Message-----
> From: Christopher Schultz [mailto:chris@christopherschultz.net]
> Sent: 20 October 2016 17:40
> To: Tomcat Users List
> Subject: Re: java.lang.OutOfMemoryError: PermGen space
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Jon,
>
> On 10/20/16 6:00 AM, Moore, Jon, Vodafone UK wrote:
>> 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.
>
> Are you also a Java novice as well? No judgement... I just want to adjust my level of
snark appropriately :)
>
> Java has a special heap space called the "permanent generation" (a term which becomes
less descriptive as time goes on) but basically all java.lang.Class objects loaded by the
JVM go there. The more libraries and other stuff that gets loaded, the more space in permgen
is used.
> The defaults for the size of permgen are often fairly small, and you may have to raise
them. This is especially true for applications that use large frameworks like Spring.
>
> Raising the permgen space is almost always the right decision under normal circumstances
when you get an OOME:permgen error. I would double whatever its current value is and monitor
the application for a while to see if that improves things.
>
> The only situation I know of where raising the permgen size is not the right move is
when there is a "classloader-pinning leak". That happens when you hot-deploy an application
many times, but the old versions of the application are not undeploying cleanly. This situation
is quite the rabbit-hole, so I'll stop there unless you can confirm that you do hot-deployments
without restarting Tomcat and the JVM.
>
> If you instead get OOME for other reasons, it's frequently NOT the right decision to
increase the heap size because it usually indicates that there is a memory leak in the application
and giving it more heap just means you'll wait longer between failures. Instead, the application
should be fixed to not leak memory :)
>
>> 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 ?
>
> The default depends upon the JVM and the OS.
>
>> We are running Tomcat 6.0.26 on Windows Server 2008 R2 standard and
>> JVM version is 1.6.0_20-b02
>
> Best way to find out for sure[1] is:
>
> C:\> java -XX:+PrintFlagsFinal -version 2>&1 | findstr HeapSize
>
> The two settings you are looking for are MaxHeapSize and InitialHeapSize. Those values
are in bytes, so you'll probably have to divide by 1024 a couple of times to get at the "real"
value in human-readable terms.
>
> The best way to find the default permgen size is:
>
> C:\> java -XX:+PrintFlagsFinal -version 2>&1  | findstr PermSize
>
> Hope that helps,
> - -chris
>
> [1]
> http://stackoverflow.com/questions/2915276/what-is-the-default-maximum-h
> eap-size-for-suns-jvm-from-java-se-6
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