Response mode errors

Errors detected by the other half session cannot be communicated to IMS until IMS attempts to send the reply.

At this point, errors must be communicated to IMS before the requested sync-point response is returned, because all response mode output is sent indicating RQD and EB. Errors are reflected by the return of an exception response with an optional ERP message, which might contain appropriate sense data and protocols.

The exception response or ERP FM header sense codes can cause the output message to be backed out (dequeued) or retransmitted, or they can cause the session to terminate with the message still on the queue. ERP message protocols can cause the message to be backed out (dequeued) regardless of the sense code through use of EB or can leave IMS in send state through use of CD. This latter case is only allowed if the sense code used results in the output message being dequeued or retransmitted.

An LUSTATUS - abort with EB is sent as the next output on the session if CD is used on the ERP message and the sense code results in dequeuing the response mode output message. However, in all of the cases where the error is detected by the other half session, the reply message is the only resource that IMS can back out. The database updates and other messages initiated by the response mode transaction cannot be backed out by IMS.