Acknowledging receipt of synchronous callout messages

A user-written IMS Connect client must send a positive (ACK) or negative (NAK) acknowledgment message to IMS after OTMA sends a synchronous callout request message. Until the ACK or NAK message is received or the timeout interval expires for either the acknowledgment or the original request, the tpipe queue remains in a wait state (WAIT_S) and cannot send or receive any other messages.

An ACK message frees the tpipe queue to send and receive other callout messages and the IMS application program continues to wait in the dependent region until either a response to the synchronous callout message is received or the synchronous callout request times out.

A NAK message not only frees the tpipe queue, but also tells OTMA what to do with the synchronous callout request message and whether to maintain or end the current RESUME TPIPE call.

The IMS Connect client can specify one of the following options on a NAK message:

  • Discard the rejected synchronous callout request message and terminate the RESUME TPIPE connection.
  • Discard the rejected synchronous callout request message, but maintain the RESUME TPIPE connection to continue retrieving other synchronous callout request messages.
  • Keep the rejected synchronous callout request message on the tpipe queue, but terminate the RESUME TPIPE connection.