About Question enthuware.oce-ejbd.v6.2.415 :

[admin]

I am not sure I understand your question. If the session is transacted, there is no need for acknowledgement mode because the transaction success or failure will determine the status of the message. If the session is not transacted, then the subsystem needs to know what measures is it allowed to take to deliver the message. That is why the second parameter becomes important.