# Substation ES in a CICSplex Environment

Workload Manager (WLM) of CICSplex SM uses the dynamic routing program `EYU9XLOP` to route eligible work requests from a requesting region to a suitable target region selected at the time the transaction is initiated.

Together with the `EYU9XLOP` routine, Substation ES handles the dynamic routing of the following requests:

- Eligible `EXEC CICS START` requests that are not associated with a terminal.
- DPL requests that are received through EXCI client programs or any function that issues an `EXEC CICS LINK PROGRAM` request.

The following figure illustrates the architecture in a CICSplex environment:

Architecture in a CICSplex Environment

Substation ES is configured to interface to Terminal Owning Region (TOR) or Application-Owning Region (AOR) through EXCI. The CICSplex can route the transaction to the proper AOR in CICSplex with `EYU9XLOP`.

If CICSplex is set up with the proper resources in each AOR, CICSplex directs the transaction to the proper AOR for execution and returns Communications Area or Container to the originating CICS, which in turn returns the user data to Substation ES.

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