Also Manik, I've read this sentence in the "clustering guide draft": It achieves this (readers that don't block writers, writers that fail-fast) by using data versioning and copying for concurrent writers. The theory is that readers continue reading shared state, while writers copy the shared state, increment a version id, and write that shared state back after verifying that the version is still valid (i.e., another concurrent writer has not changed this state first). I guess it refers to R_R behaviour ( and not R_C ), but again, is there any other reason (tx concurrency) to abort a transaction or restart it ?? View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4224446#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...