Thanks for this Chuck. I realise now what is happening. I thought the PermGen space was used in the heap when now I see it as just storing class definitions. So I could reduce it below 128Mb if I choose. Is there a default value?
As to setting Xms and Xmx to the same, I will do that. A job hung earlier and I wonder if memory was to blame although there is nothing in the system or server logs to say so. -----Original Message----- From: Caldarale, Charles R [mailto:chuck.caldar...@unisys.com] Sent: 09 Dec 2011 14 46 To: Tomcat Users List Subject: RE: Tomcat memory allocation > From: Martin O'Shea [mailto:app...@dsl.pipex.com] > Subject: Tomcat memory allocation > Following advice found elsewhere on the internet Always to be taken with large chunks of salt. > set JAVA_OPTS=%JAVA_OPTS% -Xms128m -Xmx512m -XX:MaxPermSize=128m You would be better off using CATALINA_OPTS, since setting JAVA_OPTS pointlessly affects the shutdown script as well as the startup one. > I know that settings: > Xms128m -Xmx512m > Control the initial heap size and what it can expand to. In a server environment, you normally want Xms and Xmx set to the same value to avoid heap thrashing. The exact size is completely dependent on what your webapps need. > But what exactly is: > -XX:MaxPermSize=128m It's the amount of space to which the so-called permanent generation can expand. PermGen holds primarily instances of java.lang.Class, so it only needs to be specified if you have a large number of classes in your environment. > Should it be set to an addition of the other settings, or the other > settings to an addition of it? What does that question mean? PermGen size is completely independent of the heap size. Make sure you have enough RAM available on the system to support the Xmx + PermGen + a_lot_of_other_stuff. Monitor the system to make sure you're not getting into paging. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
