CICS services for application

CICS® applications execute under CICS control, using CICS services and interfaces to access programs and files.

Application programming interface

You use the application programming interface or API to access CICS services from the application program. You write a CICS program in much the same way as you write any other program. Most of the processed logic is expressed in standard language elements, but you can use CICS commands to request CICS services.

Terminal control services

These services allow a CICS application program to communicate with terminal devices. Through these services, information may be sent to a terminal screen and the user input may be retrieved from it. It's not easy to deal with terminal control services in a direct way. Basic Mapping Support, or BMS, lets you communicate with a terminal with a higher language level. It formats your data, and you do not need to know the details of the data stream.

File and database control services

We may differentiate the following two different CICS data management services:

CICS file control offers you access to data sets that are managed by either the Virtual Storage Access Method (VSAM) or the Basic Direct Access Method (BDAM). CICS file control lets you read, update, add, and browse data in VSAM and BDAM data sets and delete data from VSAM data sets.
Database control lets you access IMS and DB2® databases. Although CICS has two programming interfaces to IMS, using the higher-level EXEC DL/I interface is recommended. CICS has one interface to DB2: the EXEC SQL interface. The EXEC SQL interface offers powerful statements for manipulating sets of tables, thus relieving the application program of record-by-record processing.

Other CICS services

Task control can be used to control the execution of a task. You may suspend a task or schedule the use of a resource by a task by making it serially reusable. Also, the priority assigned to a task may be changed.
Program control governs the flow of control between application programs in a CICS system. The name of the application referred to in a program control command must have been defined as a program to CICS. You can use program control commands to link one of your application programs to another, and transfer control from one application program to another, with no return to the requesting program.
Temporary Storage (TS) and Transient Data (TD) control. The CICS temporary storage control facility provides the application programmer with the ability to store data in temporary storage queues, either in main storage or in auxiliary storage on a direct-access storage device, or, in the case of temporary storage, the coupling facility. The CICS transient data control facility provides a generalized queuing facility to queue (or store) data for subsequent or external processing.
Interval control services provide functions that are related to time. Using interval control commands, you can start a task at a specified time or after a specified interval, delay the processing of a task, and request notification when a specified time has expired, among other actions.
Storage control facility controls requests for main storage to provide intermediate work areas and other main storage needed to process a transaction. CICS makes working storage available with each program automatically, without any request from the application program, and provides other facilities for intermediate storage both within and among tasks. In addition to the working storage provided automatically by CICS, however, you can use other CICS commands to get and release main storage.
Dump and trace control. The dump control provides a transaction dump when an abnormal termination occurs during the execution of an application program. CICS trace is a debugging aid for application programmers that produces trace entries of the sequence of CICS operations.