If you are after propagation between VM instances then you need to either use JTS (also supports JTA) or Web Services transactions. The default JTA implementation is purely local, i.e., within a single VM.
But I've changed jbossjta-properties.xml to this:
<property name="com.arjuna.ats.jta.jtaTMImplementation" value="com.arjuna.ats.internal.jta.transaction.jts.TransactionManagerImple"/> <property name="com.arjuna.ats.jta.jtaUTImplementation" value="com.arjuna.ats.internal.jta.transaction.jts.UserTransactionImple"/>
Anything else I have to do to use Transactions as JTA?
I assume you mean "Transactions as JTS" since the JTA is the default in 4.2 and thus you don't need to do any changes for JTA.
For JTS: Have you actually installed the JTS? It does not ship with AS 4.2. It's not even guaranteed to work on AS 4.2 at the moment, but you won't know for sure until you download it and try it. The integration procedure is not documented yet, but take a look at the installation notes for adding JTS to previous versions of JBossAS, they will probably provide some useful direction.