How to increase Java heap space for a tomcat app

Question

There are lots of questions that ask this or a similar question.

They all give the command that has to be executed, what I don't understand is where do I write this command. I want to permanently increase the heap space for my tomcat apps.

I read this page http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html and it says under the Tomcat section

Stop Tomcat server, set environment variable CATALINA_OPTS, and then restart Tomcat. Look at the file tomcat-install/bin/catalina.sh or catalina.bat for how this variable is used. For example,

set CATALINA_OPTS=-Xms512m -Xmx512m (Windows, no "" around the value)
export CATALINA_OPTS="-Xms512m -Xmx512m" (ksh/bash, "" around the value)
setenv CATALINA_OPTS "-Xms512m -Xmx512m" (tcsh/csh, "" around the value)

So I replaced the line

set CATALINA_OPTS=

with

set CATALINA_OPTS=-Xms512m -Xmx512m

But I still get the error.

javax.servlet.ServletException: Servlet execution threw an exception

root cause

java.lang.OutOfMemoryError: Java heap space java.lang.reflect.Array.multiNewArray(Native Method) java.lang.reflect.Array.newInstance(Array.java:90) nom.tam.util.ArrayFuncs.newInstance(ArrayFuncs.java:1028) nom.tam.fits.ImageData.read(ImageData.java:259) nom.tam.fits.Fits.readHDU(Fits.java:573) controller.UploadServlet.retreiveFITSFileFields(UploadServlet.java:206) controller.ScanServerFiles.doPost(ScanServerFiles.java:39) javax.servlet.http.HttpServlet.service(HttpServlet.java:637) javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

Answer 1

First of all you cannot change the memory settings only for a tomcat application but rather for all tomcat instance.

If you are running tomcat from console (using startup.bat) you'll need to edit catalina.bat and play around with CATALINA_OPTS. For example:

set CATALINA_OPTS=-Xms512m -Xmx512m

Restarting tomcat will apply the new settings.

If you are still getting OutOfMemoryError you need to know how much memory does your application need at that particular moment (nom.tam.util.ArrayFuncs...). You'll either have to optimize the application or simply increase the memory provided to tomcat.

Answer 2

Your change may well be working. Does your application need a lot of memory - the stack trace shows some Image related features.

I'm guessing that the error either happens right away, with a large file, or happens later after several requests.

If the error happens right away, then you can increase memory still further, or investigate find out why so much memory is needed for one file.

If the error happens after several requests, then you could have a memory leak - where objects are not being reclaimed by the garbage collector. Using a tool like JProfiler can help you monitor how much memory is being used by your VM and can help you see what is using that memory and why objects are not being reclaimed by the garbage collector.

Answer 3

There is a mechanism to do it without modifying any files that are in the distribution. You can create a separate file %CATALINA_HOME%\bin\setenv.bat or $CATALINA_HOME/bin/setenv.sh and put your environment variables there. Further, the memory settings apply to the JVM, not Tomcat, so I'd set the JAVA_OPTS variable instead:

set JAVA_OPTS=-Xmx512m