# Security Considerations

The user identifier under which the program executes is the same as the parameter `USERID` defined in the CICS interface parameters member. The transaction identifier under which the program executes depends on the Substation ES recipe, as follows:

- If the recipe does not specify Mirror Tran, the program runs under the Substation ES default transaction `SXEX`.
- If the recipe specifies Mirror Tran and User Tran is set to `N`, the program runs under Mirror Tran.
- If the recipe specifies Mirror Tran and User Tran is set to `Y`, the program starts under CSMI and then runs under Mirror Tran.

Your security system must allow the program and transaction to execute. You might have to add or modify security definitions for proper program execution to occur.

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