Tip: Keep a ‘last known good’ config.xml file on your admin node.
With even a small cluster, anytime a change to a setting in the Weblogic console causes a bad write-out to this file (like almost every other time!), all you have to do to recover is copy your last known good config.xml file over the faulty one, create an empty file named REFRESH on each node (including admin) and rename all of the ../WebCTDomain/server/ directories (all nodes, including admin) so that a new /server directory gets created.
It shouldn’t happen. It sounds goofy. But it’s a lifesaver when you need it!
*In some cases the Vista_WLSstore database table also needs to be renamed so that it gets recreated on application startup.