How external subsystems are specified to IMS

In an IMS.PROCLIB member, define all external subsystems that are to be accessed by IMS applications. The EXEC statement of the control region points to this member with the SSM parameter.

For each external subsystem defined to IMS, specify in the IMS.PROCLIB member:

  • The external subsystem type
  • The z/OS® name of the external subsystem
  • The name of the external subsystem module table (ESMT) that specifies the modules in the external subsystem attachment package (ESAP)
  • The language interface token (LIT) that IMS uses to route application calls to the external subsystem
  • The name of a resource translation table (RTT) supplied by the external subsystem, if needed, to identify the external resources required by IMS application programs
  • The command recognition character (CRC) that IMS uses to route operator commands to the external subsystem
  • The region error option (REO) code indicating the action to be taken when application calls to the external subsystem cannot be processed. When a Resource Translation Table (RTT) is used, the OPTION value specified in the RTT overrides the REO option in the SSM member.

You must also supply the external subsystem-supplied tables (ESMT and RTT) in the appropriate load module library.

You have the option to supply external subsystem definitions for dependent regions. If the SSM EXEC parameter is not specified for these types of dependent regions, the region can access all subsystems defined to the control region. If the SSM EXEC parameter is specified, the dependent region can access only those subsystems defined in the identified PROCLIB member. (The subsystems also must have been defined to the control region.) Use a dummy PROCLIB member (one having no definitions) if the dependent region is not to have access to any external subsystem.

Note: JMP and JBP regions can also access control-region-defined Db2 for z/OS subsystems that use the COORD=RRS parameter in the IMS.PROCLIB member. In the DFSJMP and DFSJBP procedures, add a DD statement (DFSDB2AF) that points to the Db2 for z/OS libraries.

The following tasks must be performed to attach an external subsystem to IMS.

To attach an external subsystem to IMS:

Procedure

  1. Define external subsystems to IMS:
    1. In the IMS procedure library (IMS.PROCLIB), add a member that contains the information about each external subsystem with which IMS communicates.
    2. On the EXEC statement of the IMS control region or the dependent region, specify in the SSM parameter the PROCLIB member that you created in the previous step.
      If you are using a Db2 for z/OS group name to access Db2 for z/OS databases, you must specify the group name in the EXEC statement of the dependent region. A Db2 for z/OS group name cannot be specified in the EXEC statement for the IMS control region.
  2. Define a language interface module if you want to use one other than the IMS-supplied one.
  3. In the IMS OPTIONS statement, specify whether you want tracing of the external subsystem link.
  4. For the external subsystem, provide the ESMT and optionally the RRT.
  5. Ensure that the external subsystem modules and databases used by IMS are in appropriate APF-authorized libraries.