Sync points requested on output by IMS

IMS commits the output message when the requested sync-point response is returned by the other session partner. The message might also be committed as the result of some sense codes that are returned on an exception response to the requested sync-point response.

Definition: The term commit means that the message has been successfully sent and dequeued, and sync point information has been updated as appropriate.

Use of the IMS /DEQUEUE command during a session outage while an output sync-point response is pending is considered a unilateral decision by an authorized terminal operator to commit the sending output message.

Depending upon the sense code used, IMS backs out the output message when an exception response is returned to the sync-point request or when the IMS /DEQUEUE command is issued by an authorized terminal operator before IMS requests a sync-point response.

Definition: The term backout means that a recoverable message is returned to the message queue (unless dequeued by a /DEQUEUE command) for subsequent retransmission. An irrecoverable message is either dequeued or returned to the message queue for subsequent retransmission, depending upon the type of error. Normally, an exception response or IMS failure causes an irrecoverable message to be dequeued. Some session failures that do not result from a subsystem failure cause an irrecoverable message to be retransmitted at the first opportunity after resynchronization. Backout results in resetting the associated DFC and ATTACH states to those of the last sync point.