The EJB container automatically handles JMS message acknowledgment for message-driven EJBs. When a message-driven EJB is deployed with the Required transaction attribute, the container acknowledges the message when the transaction commits.
A message-driven EJB deployed as NotSupported or with bean-managed transactions uses AUTO_ACKNOWLEDGE. Like other asynchronous JMS message consumers, the acknowledgment is performed when the onMessage method returns.
Message-driven beans may also specify the DUPS_OK_ACKNOWLEDGE mode with the <jms-acknowledge-mode> tag in the ejb-jar.xml deployment descriptor. This acknowledgment mode enables the underlying JMS implementation to lazily acknowledge messages.
DUPS_OK_ACKNOWLEDGE performs ...