# Requests or Replies

Requests or replies occur in both the CICS and IMS environments.

The following figure shows the request or reply message flow:

1. Either TIBCO BusinessWorks (1) or another TIBCO messaging client application (2) initiates a request that is passed to a messaging daemon or EMS server (3). The request is denoted by solid arrows.
2. The daemon or EMS server (3) forwards the request to Substation ES, where ESB Interface (4) receives and transforms the message data and sends it to the appropriate interface (5).
3. The interface (5) delivers the request to the application in the back-end system (BES). In this example, the delivery is to Applications 1 and 2 (6 and 7) within the z/OS environment.
4. Applications 1 and 2 (6 and 7) return a result set or acknowledgment, as denoted by the dotted arrows that return to the applications that initiate the request.

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