# IMS Interface

Substation ES IMS Interface establishes the connection and enables communication to IBM's IMS transaction processing system.

Substation ES IMS Interface is a multithreaded application that executes in the same address space as the host side of Substation ES. One Substation ES IMS interface can have many concurrent subtasks (OTMA clients) communicating with an IMS Transaction Manager (TM).

You set the number of threads that can be concurrently opened and other IMS connectivity settings and Substation ES required parameters. Set them at startup by specifying the values for the system initialization parameters (SIPs) for IMS Interface. For more information, see TIBCO Substation ES Installation and Administration.

You can configure multiple Substation ES IMS interfaces that will execute concurrently from a single Substation ES. Each such interface can simultaneously communicate with one or more IMS TMs.

ESB Interface can optionally perform data transformation when it receives a request or reply from an external application. When the ESB Interface processing is completed, it signals to IMS Interface that a request can be processed. Subsequently, the request, along with contents received from the TIBCO messaging application, is validated and packaged into an OTMA message by Substation ES OTMA Interface.

Substation ES IMS Interface can also receive data from the IMS TM applications. The data is processed as follows:

1. Forwarded as buffers (IOAREA) by the applications to an I/O Program Communication Block (IOPCB) or alternate IOPCB.
2. If used, redirected by the IMS OTMA prerouting exit.
3. Delivered to Substation ES IMS Interface by OTMA using XCF.

The OTMA message is forwarded for transformation and finally delivered to an awaiting TIBCO messaging application. When a reply is required from a TIBCO messaging application, the response is delivered as a normal inbound transaction call except the payload is delivered to the requestor data area.

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