Tomcat kept running out of memory when running it as a service from within Eclipse. Following is a solution:

Double-click on your Tomcat service under the Servers tab, and click on the "Open launch configuration" to open the Tomcat launch configuration window. On the Arguments tab, append the two following lines in the "VM arguments" form window:

-XX:MaxPermSize=128m
-Xmx1024m

How-to on running Tomcat within Eclipse:

• Eclipse Help: Creating a server
• IBM: Developing Web applications with Tomcat and Eclipse