I've run into another issue. When memory is running short, the server side callback handler has the ability to persist callbacks to secondary storage. Currently, there is one true persisting callback store, which I guess predates jboss serialization, since it uses java serialization. Therefore, it can't handle some Messaging callbacks. Extending it to use jboss serialization shouldn't be a problem. However, Tom mentioned that, at Tim's request, he implemented a BlockingCallbackStore, which simply blocks the thread passing calllbacks to Remoting. So I'm wondering what the Messaging philosophy here. Do you want to have the option to configure a true persisting callback store? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3975196#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...