IMS DB (Information Management System Database), is a hierarchical database management system (DBMS) developed by IBM. It was initially introduced in the 1960s and has since evolved into one of the primary mainframe database systems used for large-scale transaction processing applications.

IMS DB follows a hierarchical data model, where data is organized in a tree-like structure, with parent-child relationships between data elements. The fundamental unit of data in IMS DB is the segment, which represents a logical grouping of related fields or attributes. Segments are organized hierarchically, with parent segments containing child segments, allowing for the representation of complex relationships between data elements.
IMS DB is widely used in industries such as banking, finance, telecommunications, and healthcare, where high-performance transaction processing and data integrity are critical requirements. It provides features such as concurrency control, data integrity mechanisms, and robust recovery facilities to ensure the reliability and availability of data in mission-critical applications.

In addition to its hierarchical database model, IMS DB also includes a set of programming interfaces and utilities that allow developers to interact with and manage IMS databases. These interfaces include the DL/I (Data Language/I) access method, which provides a powerful and flexible means of accessing and manipulating IMS DB data from application programs written in languages such as COBOL and PL/I.