Now totally clueless. Found the example definition of an oracle XA datasource in the docs\examples\jca folder of JBOss As and adapted it: <xa-datasource> | <jndi-name>Oracle</jndi-name> | <track-connection-by-tx/> | <isSameRM-override-value>false</isSameRM-override-value> | <xa-datasource-class>oracle.jdbc.xa.client.OracleXADataSource</xa-datasource-class> | <xa-datasource-property name="URL">jdbc:oracle:thin:@172.31.10.32:1521:xe</xa-datasource-property> | <xa-datasource-property name="User">eadb</xa-datasource-property> | <xa-datasource-property name="Password">oracle</xa-datasource-property> | <!-- Uses the pingDatabase method to check a connection is still valid before handing it out from the pool --> | <!--valid-connection-checker-class-name>org.jboss.resource.adapter.jdbc.vendor.OracleValidConnectionChecker</valid-connection-checker-class-name--> | <!-- Oracles XA datasource cannot reuse a connection outside a transaction once enlisted in a global transaction and vice-versa --> | <no-tx-separate-pools/> | <!-- Checks the Oracle error codes and messages for fatal errors --> | <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.OracleExceptionSorter</exception-sorter-class-name> | | <!-- corresponding type-mapping in the standardjbosscmp-jdbc.xml (optional) --> | <metadata> | <type-mapping>Oracle9i</type-mapping> | </metadata> | </xa-datasource> | | <mbean code="org.jboss.resource.adapter.jdbc.vendor.OracleXAExceptionFormatter" | name="jboss.jca:service=OracleXAExceptionFormatter"> | <depends optional-attribute-name="TransactionManagerService">jboss:service=TransactionManager</depends> | </mbean> | but this results in this exception: 08:20:32,745 INFO [STDOUT] Hibernate: select experiment0_.ExperimentID as Experime1_76_, experiment0_.Size as Size76_, experiment0_.SowingYear as SowingYear76_, experiment0_.Description as Descript4_76_, experiment0_.HarvestYear as HarvestY5_76_, experiment0_.SowingDate as SowingDate76_, experiment0_.AddressCode as AddressC7_76_, experiment0_.AddressFAOCode as AddressF8_76_, experiment0_.PartnerCode as PartnerC9_76_, experiment0_.ProjectCode as Project10_76_, experiment0_.ExperimentCode as Experim11_76_, experiment0_.ExperimentName as Experim12_76_, experiment0_.SiteID as SiteID76_, experiment0_.HarvestDate as Harvest14_76_, experiment0_.Design as Design76_, experiment0_.Samples as Samples76_, experiment0_.Replications as Replica17_76_ from EXPERIMENT experiment0_ limit ? | 08:20:32,916 ERROR [XAManagedConnectionFactory] Start transaction failed for org.jboss.resource.adapter.jdbc.xa.XAManagedConnection@1e3cf1f | 08:20:32,916 WARN [TxConnectionManager] Connection error occured: org.jboss.resource.connectionmanager.TxConnectionManager$TxConnectionEventListener@1e23cfc[state=NORMAL mc=org.jboss.resource.adapter.jdbc.xa.XAManagedConnection@1e3cf1f handles=0 lastUse=1184653232885 permit=true trackByTx=true mcp=org.jboss.resource.connectionmanager.JBossManagedConnectionPool$OnePool@133066c context=org.jboss.resource.connectionmanager.InternalManagedConnectionPool@eac619 xaResource=org.jboss.resource.connectionmanager.xa.JcaXAResourceWrapper@11c55b txSync=null] | oracle.jdbc.xa.OracleXAException | at oracle.jdbc.xa.OracleXAResource.checkError(OracleXAResource.java:1157) | at oracle.jdbc.xa.client.OracleXAResource.start(OracleXAResource.java:295) | at org.jboss.resource.adapter.jdbc.xa.XAManagedConnection.start(XAManagedConnection.java:121) | at org.jboss.resource.connectionmanager.xa.JcaXAResourceWrapper.start(JcaXAResourceWrapper.java:113) | at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.enlistResource(TransactionImple.java:701) | at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.enlistResource(TransactionImple.java:446) | at org.jboss.resource.connectionmanager.TxConnectionManager$TxConnectionEventListener$TransactionSynchronization.enlist(TxConnectionManager.java:773) | at org.jboss.resource.connectionmanager.TxConnectionManager$TxConnectionEventListener.enlist(TxConnectionManager.java:564) | at org.jboss.resource.connectionmanager.TxConnectionManager.managedConnectionReconnected(TxConnectionManager.java:337) | at org.jboss.resource.connectionmanager.BaseConnectionManager2.reconnectManagedConnection(BaseConnectionManager2.java:518) | at org.jboss.resource.connectionmanager.BaseConnectionManager2.allocateConnection(BaseConnectionManager2.java:399) | at org.jboss.resource.connectionmanager.BaseConnectionManager2$ConnectionManagerProxy.allocateConnection(BaseConnectionManager2.java:842) | at org.jboss.resource.adapter.jdbc.WrapperDataSource.getConnection(WrapperDataSource.java:88) | at org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider.getConnection(InjectedDataSourceConnectionProvider.java:47) | at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:423) | at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144) | at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:139) | Can anyone tell me what is wrong? And given the fact that XA is necessary, where to find an example for mysql? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4064840#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...