IMS DB is first database management system which is created by IBM. IMS databases are hierarchical in other words it contains tree structures.

In 1966, 12 members from American Rockwell & Caterpillar Tractor teams began to start designing Information Control System and Data Language (ICS & DL/I).

The IBM team completed the first release of ICS in 1967. In 1969, ICS renamed as Information Management System (IMS) and released to outside world.

All access is through the predefined paths which are created in the tree structure. IMS DB is highly structured database. All access to IMS database is through the interface modules called DL/I.

The DL/I interface must be called for every time reading or updating a database. There are two types of access method, which defines how the database is structured.

The first type is TSO access method and the second type of access method is the MVS access method. The IMS database manager provides different ways for IMS databases to be accessed, Including DLI mode and BMP mode.

In most cases, IMS databases are defined as VSAM datasets. IMS comes equipped with complete backup and recovery utilities. In addition the VSAM utility, IDCAMS, can be used on database which has been defined as VSAM.

The physical elements on an application system that use IMS are shown in the following figure. The data in each level is dependent on the data in the next higher level.

The data is well arranged and organized. Because of this the integrity is ensured, and the storage and retrieval process is optimized.