Specifying the SSM EXEC parameter

Specifying the SSM EXEC parameter

Specify the SSM EXEC parameter in the start up procedure of the IMS control region. This parameter specifies the one-character to four-character subsystem member name (SSM).
If you specify the SSM for the IMS control region, any dependent region running under the control region can attach to the WebSphere MQ queue manager named in the IMS.PROCLIB member specified by the SSM parameter. The IMS.PROCLIB member name is the IMS ID (IMSID=xxxx) concatenated with the one to four characters specified in the SSM EXEC parameter. The IMS ID is the IMSID parameter of the IMSCTRL generation macro.
IMS lets you define as many external subsystem connections as are required. More than one connection can be defined for different WebSphere MQ queue managers. All WebSphere MQ connections must be within the same z/OS system. For a dependent region, we can specify a dependent region SSM or use the one specified for the control region. We can specify different region error options (REOs) in the dependent region SSM member and the control region SSM member. Table 13 shows the different possibilities of SSM specifications.
Table 13. SSM specifications options

SSM for control region SSM for dependent region Action Comments

No No None No external subsystem can be connected.
No Yes None No external subsystem can be connected.
Yes No Use the control region SSM Applications scheduled in the region can access external subsystems identified in the control region SSM. Exits and control blocks for each attachment are loaded into the control region and the dependent region address spaces.
Yes Yes (empty) No SSM is used for the dependent region Applications scheduled in this region can access DL/I databases only. Exits and control blocks for each attachment are loaded into the control region address space.
Yes Yes (not empty) Check the dependent region SSM with the control region SSM Applications scheduled in this region can access only external subsystems identified in both SSMs. Exits and control blocks for each attachment are loaded into the control region and the dependent region address spaces.

There is no specific parameter to control the maximum number of SSM specification possibilities.

SSM for control region	SSM for dependent region	Action	Comments
No	No	None	No external subsystem can be connected.
No	Yes	None	No external subsystem can be connected.
Yes	No	Use the control region SSM	Applications scheduled in the region can access external subsystems identified in the control region SSM. Exits and control blocks for each attachment are loaded into the control region and the dependent region address spaces.
Yes	Yes (empty)	No SSM is used for the dependent region	Applications scheduled in this region can access DL/I databases only. Exits and control blocks for each attachment are loaded into the control region address space.
Yes	Yes (not empty)	Check the dependent region SSM with the control region SSM	Applications scheduled in this region can access only external subsystems identified in both SSMs. Exits and control blocks for each attachment are loaded into the control region and the dependent region address spaces.