Hi, I are using Jboss 4.0.5 GA as the application server and wanted to see if someone can provide some insight into how messages ID's are generated in a cluster. I am seeing issues when Jboss MQ server is configured in a cluster where messages are persisted in Oracle. Duplicate message id's are getting generated in the nodes in a cluster when this happens. The messages aren't persisted at this point and fail with the following error. Caused by: org.jboss.mq.SpyJMSException: Could not store message: 3 msg=87 hard NOT_STORED PERSISTENT queue=QUEUE.ppmLightServiceQueue priority=4 lateClone=false hashCode=1363363; - nested throwable: (java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (ITG.SYS_C007015) violated) at org.jboss.mq.pm.jdbc2.PersistenceManager.add(PersistenceManager.java:1097) at org.jboss.mq.server.PersistentQueue.addMessage(PersistentQueue.java:58) at org.jboss.mq.server.JMSQueue.addMessage(JMSQueue.java:180) at org.jboss.mq.server.JMSDestinationManager.addMessage(JMSDestinationManager.java:415) at org.jboss.mq.server.JMSDestinationManager.addMessage(JMSDestinationManager.java:399) at org.jboss.mq.server.JMSServerInterceptorSupport.addMessage(JMSServerInterceptorSupport.java:106) at org.jboss.mq.security.ServerSecurityInterceptor.addMessage(ServerSecurityInterceptor.java:168) at org.jboss.mq.server.TracingInterceptor.addMessage(TracingInterceptor.java:226) at org.jboss.mq.server.JMSServerInvoker.addMessage(JMSServerInvoker.java:112) at org.jboss.mq.il.uil2.ServerSocketManagerHandler.handleMsg(ServerSocketManagerHandler.java:111) at org.jboss.mq.il.uil2.SocketManager$ReadTask.handleMsg(SocketManager.java:395) at org.jboss.mq.il.uil2.msgs.BaseMsg.run(BaseMsg.java:398) at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:748) at java.lang.Thread.run(Thread.java:619) Caused by: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (ITG.SYS_C007015) violated at oracle.jdbc.driver.SQLStateMapping.newSQLException(SQLStateMapping.java:85) at oracle.jdbc.driver.DatabaseError.newSQLException(DatabaseError.java:112) at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:173) at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:455) at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:413) at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:1030) at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:194) at oracle.jdbc.driver.T4CPreparedStatement.executeForRows(T4CPreparedStatement.java:947) at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1222) at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3381) at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:3462) at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeUpdate(OraclePreparedStatementWrapper.java:1349) at org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeUpdate(WrappedPreparedStatement.java:251) at org.jboss.mq.pm.jdbc2.PersistenceManager.add(PersistenceManager.java:1136) at org.jboss.mq.pm.jdbc2.PersistenceManager.add(PersistenceManager.java:1082) ... 13 more Is there a configuration parameter that can be changed to avoid duplicate messages being generated in a cluster. In Conclusion: Since the JMS publisher is an HA Singleton, it may switch node from time to time. The zero start value is hardcoded in the JBoss 4.0.5GA messaging code, in org.jboss.mq.server.JMSDestination: //Counter used to number incomming messages. (Used to order the messages.) long nextMessageIdCounter = 0; protected long nextMessageId() { <snip> } So the way to fix this is to modify org.jboss.mq.server.JMSDestination.nextMessageId() to return a message id generated from the current system clock. Can someone suggest if this is the right approach for this problem. I see that this is something basic which a HA application should cater to that I need to understand. Can someone shed some light into this? Regards, Suresh