WAS - How to clear the WebSphere class caches

This is something for which I've not yet had a requirement, but one day, my son, one day :-)

Problem

Instructions on clearing the java class caches in IBM WebSphere Application Server. Both the JVM's shared class cache and WebSphere Application Server's OSGi class cache.

Resolving the problem

IBM Support may ask you to clear the class cache. There are several reasons for this. After an upgrade, it is possible that the class cache's are still holding onto previous versions of classes. It is also possible that the caches became corrupted.

Please remember there are two caches that will need to be cleared, the JVM's cache and the OSGi cache. The server has to be stopped before clearing the cache.

Technote - How to clear the WebSphere class caches