Data management for the Advanced Toroidal Facility (ATF), a stellarator located at Oak Ridge National Laboratory, is provided by DMG, a locally developed, VAX‐based software system. DMG is a data storage and retrieval software system that provides the user interface to ATF raw and analyzed data. Data are described in terms of data models and data types and are organized as signals into files, which are internally documented. The system was designed with user accessibility, software maintainability, and extensibility as primary goals. Extensibility features include compatibility with ATF as it moves from pulsed to steady‐state operation and capability for use of the DMG system with experiments other than ATF. DMG is implemented as a run‐time library of routines available as a shareable image. General‐purpose and specialized data acquisition and analysis applications have been developed using the DMG system. This article describes the DMG system and the interfaces to it.