an optional declaration of the acknowledgment mode for the message-driven bean if bean-managed transaction demarcation is used (ie. self.transactionType = Bean)

The acknowledge-mode specifies whether JMS AUTO_ACKNOWLEDGE or DUPS_OK_ACKNOWLEDGE message acknowledgment semantics should be used for the onMessage message of a message-driven bean that uses bean managed transaction demarcation.

The acknowledge-mode must be one of the two following:  Auto-acknowledge, Dups-ok-acknowledge