RED CICS Request/Reply
CICS RED provides a server module that user application can link to the called SXXREQR which provides an immediate synchronous method.
SXXREQR is a reentrant safe thread and an open API, and accessible by multiple transactions concurrent without locking issues.
SXXREQR runs on L8/L9 TCBs and receives parameters from the user application having to do with the following items:
The flow is listed as follows:
- User application sets up message data in the following items:
- User application sets up the SXXREQR parameter information.
- User application does CICS LINK to SXXREQR.
- SXXREQR sends the message immediately to Substation ES. If no Substation ES is available, an error is immediately generated and returned to caller.
- The Substation ES accepts the message, and then sends it to its destination based on the Service definition it has. The message contains a TOKEN (tibss-envelope) that must be added to the response message. The response message along with the token are sent back to Substation ES on the "reply-to" destination.
- If Substation ES fails, SXXREQR returns an error condition to the caller.
- User application reviews a return code and a reason code for any error indication.
- On normal return (for example, no errors and zero return code), user application uses response data as indicated from Container, TSQ, CommArea, or Data location.
The following figure shows how the Substation RED synchronous transfers:
- Request/Reply Message Flows in CICS
When SXXREQR receives control, it does a series of steps.
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