You'll see org.jboss.cache.TimeoutException. Exactly where depends on which lock stripes conflict. An example is the stack trace in your post in the middle of this page: http://www.jboss.org/index.html?module=bb&op=viewtopic&t=151524&a... That particular stack trace has to do with the timestamps cache used with query caching and can be avoided by not using query caching or putting the timestamps in their own cache. But a similar thing could happen with two entities or collections that happen to hash to the same lock stripe. Same exception but the stack trace would run through the beforeCompletion() method of org.jboss.cache.interceptors.TxInterceptor.LocalSynchronizationHandler or RemoteSynchronizationHandler. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4221359#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...