The CICS application programming interface

In CICS® programs, most of the processing logic is expressed in standard language statements, but to access program resources that are managed by CICS and to request CICS services, you use the CICS application programming interface (API).

The CICS API provides a rich set of commands that you can use to write applications that support your business and that make best use of the environment provided by CICS. At the same time, the API shields you from the complexities of managing the transaction processing environment, leaving you to focus on the business.

The EXEC CICS command format

This format uses commands with the following general syntax to request CICS services.
EXEC CICS commandname <option> <option> ...

You can use this format in programs written in COBOL and C languages.

The CICS application programming interface (API) provides access to a rich set of CICS services that you can use to construct sophisticated applications consisting of many interacting programs.

CICS programs that use the CICS API can perform the following operations.
  • Access data held in VSAM files.
  • Communicate with a variety of terminals and devices, including printers, in your communication network.
  • Connect to programs on other platforms that use TCP/IP protocols.
  • Exchange data with other programs in the same transaction and with other transactions.

CICS programs can manage their own storage to provide intermediate work areas and other main storage needed to process a transaction; they can handle exceptional conditions and failures; and they can capture data to help you diagnose problems.

CICS programs run as part of a transaction under the control of a CICS task and can perform the following actions.
  • Obtain information about the program's environment.
  • Initiate® other transactions immediately or in the future.
  • Commit or roll back the current unit of work.
  • Reserve and relinquish locks on resources that are shared with other tasks.
  • Adjust the priority of the task and relinquish control in favor of other tasks that have a higher priority.
  • Identify and authenticate users that initiate transactions using the services of the external security manager.
  • Capture data in journals that can be used to reconstruct events or data changes.
  • Interact with the operating system.

CICS TX supports a subset of APIs that are supported by CICS Transaction Server for z/OS®.