An attempt to enlist two Oracle connections causes the second enlistResource to fail with an exception similar to:

oracle.jdbc.xa.OracleXAException
at oracle.jdbc.xa.OracleXAResource.checkError(OracleXAResource.java:938)
at oracle.jdbc.xa.client.OracleXAResource.start(OracleXAResource.java:244)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.enlistResource(TransactionImple.java:902)
at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.enlistResource(TransactionImple.java:513)

Note the line number changes a bit depending on version of Oracle JDBC etc. However, the affect is always the same.

There are others who noted this problem on the forum with no resolution or reply (except my own concurring with the observation).

In particular two connections to same server using different user id's and passwords. I will test whether two completely separate oracle instances have this issue and update the bug.