IMS/VS: An evolving system

The evolution of IMS/VS described in this paper has been achieved while preserving the application program interface for both data base and terminal I/O requests. An application program written in the late 1960s for the then IMS/360 continues to run on the most recent IMS/VS release. This continuity has been the overriding objective throughout this evolution. The new facilities of IMS/VS are mainly the result of the rapid increase in the use of on-line applications by its users and the growing need for continuous operations. These trends are expected to continue in the years ahead, and the new IMS/VS facilities provide a solid base for continuing evolution in that direction.