# Prerequisites

IMS version 10 or later is necessary for interfacing with Substation ES.

Open Transaction Manager Access (OTMA) communicates with programs and other resources in IMS regions.

The following table lists the requirements that must be met for IMS regions:

Item | Description
--- | ---
IMS V10 | `APAR PK71135: IMS SYNCHRONOUS CALLOUT FUNCTION ACTIVATION`
IMS V11 | `APAR PK81543: OTMA SYNCHRONOUS CALLOUT FUNCTION ACTIVATION` `APAR/PTF PM09695/UK56450` enhances the synchronous call-out function in the following ways: OTMA issues a new NAK message with the `X'2B'` sense code when a late or invalid acknowledgment message is received. OTMA cleans the unused tpipes for ICAL after 2 IMS checkpoints. The output of the /DISPLAY TMEMBER TPIPE SYNC command is changed to display the current number of ICAL messages that OTMA received for a particular tpipe. The `NO_RSP` label is changed to `NO_COT`.
Parameter Definitions | For Substation ES to connect and execute successfully in an IMS environment, you must correctly define the following parameters for the IMS procedure of the `DB/DC` online control program:
    GRNAME=XCF group name
    OTMA=Y
    OTMAMD=Y
    OTMANM – (When specified in IMS, you must set the Substation ES
    Applid keyword value accordingly.)
    OTMASE=N
    OTMASP=Y
Permissions | Substation ES must be able to run the /STOP and /START TMEM x TPIPE y commands. Check IMS and/or SAF security settings to ensure that Substation is authorized to run these commands.

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