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DFHKCP

In CICS 2.1, DFHKCP, the CICS task control module, manages all CICS tasks. It performs the following functions:

  • create, cancel, suspend, or change the priority of a running task

  • provide enqueue/dequeue services

  • manage some transaction definition services, such as updating or deleting a transaction definition

  • browse transaction table entries

Tasks will be processed concurrently with DFHKCP allocating processor time among them. This is known as multitasking.

When an operator requests a transaction (normally by logging on and keying in a transaction code), CICS checks the status of the operator and the terminal. This ensures that the operator is known to the system, and that the transaction is valid for that user and terminal. DFHKCP then creates a task for the transaction.

CICS tries to give the best service to the most important or urgent work. Usually, several tasks are competing for resources, so a transaction, an operator and a terminal are each assigned a priority related to the importance of the functions they perform. CICS sums these priorities to give the overall priority of the task, and uses this priority to decide the order in which to process tasks.

Because transactions are not normally processed through to completion in a single, uninterrupted operation, CICS makes priority decisions many times during the execution of a task. A transaction normally executes uninterrupted until it requests services from CICS. CICS then makes a decision to return control to the requesting task or choose another for service.

DFHKCP is also called at CICS initialization to build transaction and profile table entries.

In CICS Version 3.1 and later, DFHKCP is a startup routine that passes control to either DFHXCP or DFHXCPC, and also deals with some ENQ and DEQ calls.

Hints

An application program may cause high activity in this module by issuing multiple task control commands such as:

  • EXEC WAIT EVENT

  • EXEC ENQ

  • EXEC DEQ

  • EXEC SUSPEND

Reference Sources

CICS General Information, GC33-0155.

CICS Facilities and Planning Guide, SC33-0504.

CICS/ESA Version 3.3, Diagnosis Reference, LY33-6072.