Modify Windows Tomcat Service Heap Size
If you are using the Tomcat Windows installer from the Apache website you will have to do the following to modify the heap size on the command line.
Browse to your <TOMCAT DIR>/bin on the command line.
Enter “tomcat6 //US//Tomcat6 –JvmMs XXX –jvmMx YYY”
Replace XXX with min heap size and YYY with max heap size.
Click return.
There are more arguments that you can use and can be viewed at http://tomcat.apache.org/tomcat-5.5-doc/windows-service-howto.html