What you need to know about CICS

CICS® is a transaction processing subsystem. This means that it provides services for a user to run applications online, by request, at the same time as many other users are submitting requests to run the same applications, using the same files and programs. CICS manages the sharing of resources, integrity of data, and prioritization of execution, while maintaining fast response times.

A CICS application is a collection of related programs that together perform a business operation, such as processing a product order or preparing a company payroll. CICS applications execute under CICS control, using CICS services and interfaces to access programs and files.

CICS applications are run by submitting a transaction request. The term transaction has a special meaning in CICS; CICS transactions explains the difference from the more common industry usage. Execution of the transaction consists of running one or more application programs that implement the required function. In CICS documentation you may find CICS application programs sometimes simply called programs, and sometimes the term transaction is used to imply the processing done by the application programs.

To develop and run CICS applications, you need to understand the relationship between CICS programs, transactions, and tasks. These terms are used throughout CICS documentation and appear in many programming commands.