IMS (Information Management System) is a database and transaction management system that was first introduced by IBM in 1968. Since then, IMS has gone through many changes in adapting to new programming tools and environments. IMS is one of two major legacy database and transaction management subsystems from IBM that run on mainframe MVS (now z/OS) systems. The other is CICS. It is claimed that, historically, application programs that use either (or both) IMS or CICS services have handled and continue to handle most of the world's banking, insurance, and order entry transactions.
IMS consists of two major components, the IMS Database Management System (IMS DB) and the IMS Transaction Management System (IMS TM). In IMS DB, the data is organized into a hierarchy. The data in each level is dependent on the data in the next higher level. The data is arranged so that its integrity is ensured, and the storage and retrieval process is optimized. IMS TM controls I/O (input/output) processing, provides formatting, logging, and recovery of messages, maintains communications security, and oversees the scheduling and execution of programs. TM uses a messaging mechanism for queuing requests.
IMS's original programming interface was DL/1 (Data Language/1). Today, IMS applications and databases can be connected to CICS applications and DB2 databases. Java programs can access IMS databases and services.