This topic applies only on the z/OS operating system.

Basic “listening in the controller” messaging flow

When a message-driven bean is mapped (that is, listening to) a queue, or to a topic through a durable subscription, a JMS message first enters into the WebSphere server in the controller, so we say the server is "listening in the controller" for these messages. When a message arrives, it flows through a sequence of events.

When a message has arrived on a JMS destination (queue or topic) on which a message-driven bean running is listening, the following sequence of events takes place:

  1. The WebSphere MQ JMS queue agent thread (running in the controller) browses the JMS destination. The queue agent identifies the application server on which a message-driven bean is running for that destination. The queue agent calls a Message Reference Handler (MRH) registered by the application server, to tell the server that a message has arrived on a destination on which one of its message-driven beans is listening. A message reference corresponding to this message is sent along with the call to the MRH.
  2. If the throttle high threshold value (see below) has not been exceeded, a work request corresponding to the just-browsed message is queued onto the WLM queue in the controller.
  3. The work request is dispatched to an individual servant. A ServerSession is obtained from the appropriate ServerSessionPool in that servant and, using the message reference as index, the message is destructively consumed from the JMS destination.
  4. The MDB application onMessage(Message) method is dispatched with the consumed message.
  5. When the onMessage(Message) method finishes, the servant notifies the controller that the work record has completed.



Related information
Concepts and considerations for MDB settings on z/OS
Concept topic    

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Last updated: Sep 20, 2010 11:08:29 PM CDT
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