Please refer to Java EE 5 tutorial
http://docs.sun.com/app/docs/doc/819-3669/6n5sg7cjl?a=view
Sun Java System Application Server 9.1 Update 1 >> The Java EE 5 Tutorial >> Services >> 31. The Java Message Service API >> Using the JMS API in a Java EE Application >> Managing Distributed Transactions
"When you create a session in an enterprise bean, the container ignores the arguments you specify, because it manages all transactional properties for enterprise beans. It is still a good idea to specify arguments of true and 0 to the createSession method to make this situation clear:"
-Ramesh
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