Operating the CICS Interface

In order for the CICS® user interface to perform its function, a connection must exist between it and a IBM® Connect:Direct® DTF. This facility can be local (within the same VTAM® domain) or remote (residing in another domain).

This connection is accomplished using operating system subtasks that are attached in the CICS address space at the CICS Interface startup. The subtasks perform two types of functions:

One or more Worker Subtasks (WSTs) are attached for each active link to a IBM Connect:Direct DTF. These subtasks are responsible for establishing a link to the DTF, passing commands to it, and receiving any results.

A single Controller Subtask (CST) is created to monitor the work of all WSTs in the system and perform communications functions with the user interface portion of CICS.

Initialization of the CICS Interface invokes programs that perform the following functions:

  • Acquires CICS Interface work areas, such as the signon table and work queue areas
  • Enables a task control global exit point and its associated global work area
  • Reads the configuration information from the configuration file and places that information in the global work area
  • Attaches the CST subtask
  • Checks for any DTF nodes that are to be activated at initialization and passes information to the CST task to allow it to create the appropriate WSTs and establish the link with the DTF.
Note: The CICS Interface module is also available for the interface autostart at CICS startup. When the module is in the PLTPI, you can start CICS without starting the interface by including a special DD card in the CICS startup JCL deck: //NDMINIT DD DUMMY. If present, NDMINIT will not start the interface as part of CICS initialization. The interface can then be started manually.