From the WebSphere Application Server Administration Console, select Servers > Server Types > WebSphere Application Servers > <Server running WBE> > Server Infrastructure > Java and Process Management > Process Definition > Java Virtual Machine > Generic JVM arguments.
Add -XX:MaxPermSize=??? to the generic JVM argument to set the max perm size.
Restart the application server.
After tuning the heap sizes, monitor the system to make sure that paging does not occur.