Specifying the SSM= EXEC parameter

Use the SSM= EXEC parameter to indicate which member of the IMS™ PROCLIB data set contains an entry for the external subsystem you want to attach.

Use the SSM= EXEC parameter to indicate which member of the IMS PROCLIB data set contains an entry for the external subsystem you want to attach. You can specify the SSM= EXEC parameter on the EXEC procedures of that control region, or for an MPP, BMP, IFP, JMP, or JBP-dependent region.

The SSM= EXEC parameter is required for an MPP, BMP, IFP, JMP, or JBP region when the subsystem member defines a Db2 for z/OS® group.

If the SSM= EXEC parameter is not specified when the IMS subsystem is initialized, the ESAF or RRSAF component is not activated. You can later activate the ESAF component and enable external subsystem support in one of two ways:

Shut down IMS and restart it, specifying the SSM= EXEC parameter.
Use the /START SUBSYS SSM command to inform IMS of the subsystem member. This action activates the ESAF component and attempts a connection to the external subsystems defined in the SSM member of the IMS PROCLIB data set.

Restriction: You can activate the RRSAF component and enable Db2 for z/OS support only by shutting down IMS and restarting it with the SSM= EXEC parameter specified.

For an MPP or an IFP dependent region that is currently active but not connected, you must stop and start the region for a connection for that dependent region.

When SSM= is specified for the control region, any dependent region running under the control region can attach to the external subsystems named in the member of the IMS PROCLIB data set pointed to by the SSM= parameter.

When SSM= is specified for an MPP, BMP, or IFP region, it provides a filter that determines whether a given application program running in that dependent region can access external subsystem resources. Only the subsystems defined in the subsystem member can be connected to the dependent region. If a subsystem is defined in the named dependent region member, but not in the control region member, a message is sent to the MTO during dependent region initialization and a subsystem connection is not made for this dependent region entry.

For example, if a subsystem entry for a given Db2 for z/OS subsystem exists in the named dependent region member, but not in the control region member, then a message is sent to the MTO during dependent region initialization and a subsystem connection is not made for this dependent region entry.

If SSM is specified on the control region but the installation wants a particular dependent region to be prohibited from attaching to any external subsystem, a member of the IMS PROCLIB data set must be created having no entries, and its ID specified in the dependent region. Application programs in this dependent region cannot attach to any external subsystem.

When the member of the IMS PROCLIB data set contains a null record, you receive the following informational message:

DFS3600I UNABLE TO INITIATE THE EXTERNAL SUBSYSTEM TABLE, RC=36

If an invalid member name is specified or if the record format is incorrect, no external subsystem is attached, but initialization continues. You can then enter the /START SUBSYS SSM command, specifying the correct subsystem name. If the /START SUBSYS SSM command is issued with an invalid subsystem member name, re-enter the command with a valid name.

Restriction: You cannot use the /START SUBSYS SSM command for external subsystems attached by RRSAF. If an invalid member name is specified or if the record format is incorrect, you must restart IMS with the corrected member name or record format.

If any record in the SSM member of the IMS PROCLIB data set is invalid, a DFS3600 message is issued and processing continues. Valid records allow an external subsystem to be attached. Invalid records in the SSM member of the IMS PROCLIB data set are ignored but can be corrected. Those external subsystems can be attached to the IMS control region using the /START SUBSYS command.