BMCLINK

DELTA IMS VTAM Communication provides an overview of BMCLINK communication.

The BMCLINK task must run on each CPU that has an IMS control region to be accessed by DELTA IMS. BMCLINK can be started and stopped asynchronously with IMS.

BMCLINK maintains an internal trace of all important activities. The trace is always active and can be printed on demand. It also appears in the SYSUDUMP. The minimum size of the trace table is 16 K, but this may be expanded if necessary.

A VTAM ACB is required for the DELTA IMS TSO session to communicate with BMCLINK. Parameter data specifies the ACBNAME used. It opens the VTAM ACB and permits logons. BMCLINK then waits for input from a DELTA IMS TSO user. When input is received, the PLU notifies the main BMCLINK task of the input and waits for a response to be queued.

DELTA IMS uses information you specify in the IMSID options to allocate RESLIB, prepare parameter data for the IMS region controller, and attach the DELTA IMS BMP.

The BMP determines the type of request. A user authorization exit is available from the BMP task that may inspect, alter, and reject any DELTA IMS update to an IMS control region. If an exit routine has been written and link-edited into the DLALIB data set, the load module name is specified in the IMSID basic options. If required, the user authorization exit is invoked. The exit may approve, alter, or reject the request, and the BMP acts accordingly.

BMCLINK requires a work area for moving data into and out of the IMS control region. The largest IMS command issued from a DELTA IMS TSO session must fit in this area. The area used is the IMS PSB index work area. Specify the size of this area using the PSB IOASIZE parameter. If you want to use the same BMCLINK for both DELTA IMS and EXTENDED TERMINAL ASSIST (version 2.2.01 and earlier), the IOASIZE value must be at least 1024 bytes; otherwise, the value must be at least 512 bytes. The value you specify must be the same as the corresponding value specified in the DELTA IMS global customization options.

The result of processing is tested and before and after records are written. These records are then read during IMS restart. These records can also be used for reporting.

A response that indicates success or failure of the action is generated and sent to the TSO session.

A BMCLINK BMP subtask is considered inactive when a period of time elapses since the receipt of the last transaction from any DELTA IMS TSO session. A DELTA IMS global option specifies the time, in seconds, after which the inactive BMP subtask should be terminated. This frees the IMS PST, but does not prevent another BMP subtask from being created later, if needed.