Send-only protocol for synchronous callout responses

IMS Connect clients return responses to synchronous callout requests from IMS application programs by using the send-only protocol.

The IMS Connect client specifies the send-only protocol for synchronous callout responses in the IRM_F4 field of the IRM prefix of the response message.

The send-only protocol for synchronous callout responses can include an acknowledgement to the callout response, or the acknowledgement can be disabled so the client does not need to switch to receive state after sending the response to IMS Connect.

If the client requires IMS to return an acknowledgement after IMS receives the callout response, the client can specify an L in the IRM_F4 field of the IRM message prefix. When L is specified, if delivery of the response is successful, IMS Connect returns a CSM (ACK). If delivery of the response is unsuccessful, IMS Connect returns an RSM (NAK). The client must issue an additional receive to retrieve the CSM or RSM, which could affect the performance of the client, but does not impact the return of the response to the waiting IMS application.

If the client does not require IMS to return an acknowledgement, the client can specify an M in the IRM_F4 field to disable the acknowledgements. When the acknowledgements are disabled, IMS Connect does not return an RSM message to the client.

The send-only message contains no transaction code and can contain either the response data or error information for the IMS application program. Send-only messages used for callout responses do not generate any type of output.

For user-written IMS Connect clients, code the callout response by specifying the following field values in the IRM of the response message: