See here:

http://www.jboss.org/wiki/Wiki.jsp?page=TransactionRecovery

JCA adapter should register a Recoverable with the RecoveryManager. There should be additional switches on witch Subject or SecurityDomain should be used for recovery. Regular XA connections may not have permission to do recovery and the app developer may not want to allow app connections to do recovery.

Additionally, different XAResources may need different recovery switches that are passed to XAResource.recover() For instance Informix needs only TMSTARTRSCAN while Oracle may need both TMENDRSCAN.