Websphere -- shared class cache by the JVMs

If you are running multiple JVMs inside your Websphere 6.x+ server -- you may be surprised to learn that the JVMs share Classes in a common Class cache. Before you freak -- note that only System classes, i.e. those that are part of the jre itself are the ones that are shared. Your Classes are not.

This is actually a feature of the IBM version of the jre/jdk 1.5 and onwards.

To turn this off: set the JVM argument -Xshareclasses:none

If you are getting weird class loading errors -- and cannot figure out why -- try shutting off this cache.