Customer Information Control System (CICS) is a transaction server that runs primarily on IBM mainframe systems under z/OS and z/VSE. CICS is a transaction manager designed for rapid, high-volume online processing. This processing is mostly interactive (screen-oriented), but background transactions are possible. Applications are written in a variety of languages and use CICS-supplied language extensions to interact with CICS resources such as files, database connections or to invoke functions such as web services. CICS manages the entire transaction such that if for any reason a part of the transaction fails all recoverable changes can be backed out.