When you use the JBossJTA JDBC driver, you may need to set the underlying transaction isolation level on the XA connection. Its default value is TRANSACTION_SERIALIZABLE, but you can set this to something more appropriate for your application by setting the com.arjuna.ats.jdbc.isolationLevel property to the appropriate isolation level in string form. Possible values include TRANSACTION_READ_COMMITTED and TRANSACTION_REPEATABLE_READ.