The data system for the advanced toroidal facility (ATF) is a logical extension of the system used for the Impurity Studies Experiment ISX‐B. Based on the ISX‐B concepts and hardware, it extends them to provide support for long‐pulse or steady‐state operation of ATF. The system is now network based rather than shared memory based and can dynamically add or remove processors. The hardware consists of a pair of VAX 8700 CPUs and an assortment of MicroVAX front ends. This hardware acquires all data, generates all control waveforms, and provides trending and logging services for the safety interlock and control systems. These systems are based on programmable logic controllers (PLCs) which are independent of the data system. The software consists of three major components: a master scheduling and monitoring system (SAMS) that provides synchronizing services and allocates files and memory; a signal‐based data and file management package (DMG) that provides data access services; and the ORNL CAMAC driver package. All diagnostics are supported by data acquisition and analysis software (either generic or specialized) that is based on and shared by these services.