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IMS(1) See IP Multimedia Subsystem.
(2) (IMs) Instant messages. See instant messaging.
(3) (Information Management System) An early IBM hierarchical DBMS for IBM mainframes. IMS was widely implemented throughout the 1970s under MVS and continues to be used under z/OS. IMS/DB (IMS/DataBase) is the back end database part, and either IMS/TM (IMS/Transaction Manager) or CICS provides the front end online interaction.
IMS/TM, formerly IMS/DC (IMS/Data Communications), runs each transaction in its own address space and allows for more precise tuning than CICS, which runs all transactions in a region. IMS/TM is also used to access DB2 databases, and Java applications can access IMS databases. See CICS.