if you wanted to modify a persistence.xml which has already been deployed you would have to undeploy it, unpack the ear/jar, modify the file, re-jar it, and deploy it. if, however, you just want to point the datasource name in the persistence.xml to another datasource you could try undeploying the ds which currently has that name a deploying the "new" ds which has the same name, but references a different DB. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4074941#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...