Eclipse memory settings when getting "Java Heap Space" and "Out of Memory"

Question

When trying to launch and run a flex/java project in eclipse I kept getting a "Out of Memory Exception" and "Java Heap Space" using Eclipse, Tomcat and a JRE.

While researching trying to adjust the memory settings I found three places to adjust these:

• Eclipse.ini

• The JRE Settings under Window > Preferences

• Catalina.sh or Catalina.bat

What are the differences between setting -xms and -xmx in these different places and what does is mean?

Is there any way to verify these memory settings are being set accordingly?

What are the optimal -xms and -xmx settings for a computer with 2gb of RAM?

Any other memory tips?

Thanks.

Answer 1

-xms is the start memory (at the VM start), -xmx is the maximum memory for the VM

• eclipse.ini : the memory for the VM running eclipse
• jre setting : the memory for java programs run from eclipse
• catalina.sh : the memory for your tomcat server

Answer 2

First of all, I suggest that you narrow the problem to which component throws the "Out of Memory Exception".

This could be:

1. Eclipse itself (which I doubt)
2. Your application under Tomcat

The JVM parameters -xms and -xmx represent the heap's "start memory" and the "maximum memory". Forget the "start memory". This is not going to help you now and you should only change this parameter if you're sure your app will consume this amount of memory rapidly.

In production, I think the only parameter that you can change is the -xmx under the Catalina.sh or Catalina.bat files. But if you are testing your webapp directly from Eclipse with a configured debug environment of Tomcat, you can simply go to your "Debug Configurations" > "Apache Tomcat" > "Arguments" > "VM arguments" and set the -xmx there.

As for the optimal -xmx for 2gb, this depends a lot of your environment and the number of requests your app might take. I would try values from 500mb up to 1gb. Check your OS virtual memory "zone" limit and the limit of the JVM itself.