Services for Application Programs
CICS manages its own processor storage and has its own task manager which handles execution of multiple programs and provides its own file management functions.
CICS region can start by using a CICS region job running in batch environment. CICS region job can view in spool by issuing PRE <region-name> command.
Each CICS starts as a separate z/OS address space. CICS application is a collection of related programs that together perform a business operation. CICS applications execute under CICS control, using CICS services and interfaces to access programs and files.
Application programming interface or API used to access CICS services from the application program. In the application program, CICS commands used to request CICS services. Below are the most important services provided by CICS in application programming –
- Terminal Control Services
- File Control Services
- Database Control Services
- Task Control Services
- Program Control Services
- Temporary Storage and Transient Data Control Services
- Interval Control Services
- Storage Control Services
- Dump and Trace Control Services
Terminal Control Services -
Terminal control services allow CICS application program to communicate with terminal devices. Information sent to a terminal screen and the user input may be retrieved from the terminal through these services.
It's not required to deal with terminal control services in a direct way and Basic Mapping Support or BMS used to communicate with a terminal instead of direct communication.
File Control Services -
CICS file control offers to access data sets that are managed by either the Virtual Storage Access Method (VSAM) or the Basic Direct Access Method (BDAM). CICS file control allows user to read, update, add and browse data in VSAM and BDAM data sets and delete data from VSAM data sets.
Database Control Services -
Database control allows user to access IMS and DB2 databases. CICS has recommended EXEC DL/I interface to interact IMS and one EXEC SQL interface to interact DB2.
Task Control Services -
Task control services can be used to control the execution of a task. User can suspend a task or schedule a task by making it serially reusable or change the priority of the task.
Program Control Services -
Program control services guides the control flow between application programs in a CICS system. The application name mentioned to a program control command must have been defined as a program to CICS. Program control commands can be used to link one 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 Services -
The CICS temporary storage control facility provides the ability to store data in temporary storage queues either in main or auxiliary storage on a direct-access storage device. The CICS transient data control facility provides a comprehensive queuing facility to queue data for subsequent or external processing.
Interval Control Services -
Interval control services provide functions related to time. Interval control commands used to 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 etc.
Storage Control Services -
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.
CICS provides other facilities for intermediate storage both within and among tasks. Application programmer can use other CICS commands to get and release main storage.
Dump and Trace Control Services -
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 CICS operations.