Thread dumpts attached to JBPORTAL-1879. With 5 users hitting one server, I primarily see - waiting on <0x0000002b2dad5118> (a java.util.HashMap) at org.jgroups.blocks.GroupRequest.doExecute(GroupRequest.java:502) - locked <0x0000002b2dad5118> (a java.util.HashMap) at org.jgroups.blocks.GroupRequest.execute(GroupRequest.java:193) at org.jgroups.blocks.MessageDispatcher.castMessage(MessageDispatcher.java:432) at org.jgroups.blocks.RpcDispatcher.callRemoteMethods(RpcDispatcher.java:192) at org.jgroups.blocks.RpcDispatcher.callRemoteMethods(RpcDispatcher.java:163) at org.jboss.cache.TreeCache.callRemoteMethodsViaReflection(TreeCache.java:4471) at org.jboss.cache.TreeCache.callRemoteMethods(TreeCache.java:4418) at org.jboss.cache.TreeCache.callRemoteMethods(TreeCache.java:4371) at org.jboss.cache.TreeCache.callRemoteMethods(TreeCache.java:4489) at org.jboss.cache.interceptors.BaseRpcInterceptor.replicateCall(BaseRpcInterceptor.java:110) at org.jboss.cache.interceptors.BaseRpcInterceptor.replicateCall(BaseRpcInterceptor.java:88) at org.jboss.cache.interceptors.OptimisticReplicationInterceptor.broadcastPrepare(OptimisticReplicationInterceptor.java:181) at org.jboss.cache.interceptors.OptimisticReplicationInterceptor.invoke(OptimisticReplicationInterceptor.java:90) at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:68) at org.jboss.cache.interceptors.TxInterceptor.runPreparePhase(TxInterceptor.java:887) at org.jboss.cache.interceptors.TxInterceptor$LocalSynchronizationHandler.beforeCompletion(TxInterceptor.java:1170) at org.jboss.cache.interceptors.OrderedSynchronizationHandler.beforeCompletion(OrderedSynchronizationHandler.java:75) at com.arjuna.ats.internal.jta.resources.arjunacore.SynchronizationImple.beforeCompletion(SynchronizationImple.java:114) at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.beforeCompletion(TwoPhaseCoordinator.java:247) at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.end(TwoPhaseCoordinator.java:86) at com.arjuna.ats.arjuna.AtomicAction.commit(AtomicAction.java:177) at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.commitAndDisassociate(TransactionImple.java:1382) at com.arjuna.ats.internal.jta.transaction.arjunacore.BaseTransaction.commit(BaseTransaction.java:135) at com.arjuna.ats.jbossatx.BaseTransactionManagerDelegate.commit(BaseTransactionManagerDelegate.java:87) at org.jboss.cache.interceptors.TxInterceptor.handleNonTxMethod(TxInterceptor.java:383) at org.jboss.cache.interceptors.TxInterceptor.invoke(TxInterceptor.java:174) at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:68) at org.jboss.cache.interceptors.CacheMgmtInterceptor.invoke(CacheMgmtInterceptor.java:157) at org.jboss.cache.TreeCache.invokeMethod(TreeCache.java:5919) at org.jboss.cache.TreeCache.put(TreeCache.java:3858) at org.jboss.cache.TreeCache.put(TreeCache.java:3532) at org.hibernate.cache.OptimisticTreeCache.writeLoad(OptimisticTreeCache.java:84) at org.hibernate.cache.TransactionalCache.put(TransactionalCache.java:55) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4159689#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...