Getting the classloading isolation correct solved the problem. I defined a distinct loader-repository in a jboss-app.xml in the META-INF of each ear and set <attribute name="Isolated">true</attribute> in the ear-deployer. This results in an application isolation as desired. It is not necessary to use xa-datasources - but it also works. The main problems along the way were to find which part of the application prevented the isolation (in my case it was the scheduler-plugin from outside of the scope of the loader-repository of the applications being referenced from a sar within the application). After sorting that out things were easy. It was a bit of a surprise to me that the tomcat deployer works in a scoped way ensuring web applications are isolated. This made me believe in the beginning there was no classloading issue. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4048657#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...