CICS is an online transaction processing system (OLTP) that provides a flexible interface to support transaction processing in large volumes on mainframe computers. CICS offers custom transaction management where a user writes CICS code to control and monitor transactions. CICS offers advance recovery options and ensures that transactions are rolled back appropriately when they fail.

CICS is designed primarily for usage by financial institutions and banks. CICS allows application developers to focus on business logic implementation instead of designing the internal details of communication. A CICS client sends a request to process a certain chunk of data from a terminal to the host computer which acts as the server. At the host computer, the desired processing is performed and the results are forwarded back to the terminal computer. CICS uses some data access methods such as VSAM, DL/1 and DB2 through the use of a telecommunication package such as VTAM or TCAM.