VM/370 - A Study of Multiplicity and Usefulness

It describes the virtual machine concept and its capabilities and implementation in VMl370. Two components of VMl370 are discussed the control program and the Conversational Monitor System. The usefulness of VMl370 in multiple and diverse environments is covered. New developments in VMl370 from hardware assists to system extensions, networking, and handshaking are briefly described as an introduction to the rest of the papers in this issue. The productivity of data processing professionals and other professionals can be enhanced through the use of interactive and time-sharing systems. Similarly, system programmers can benefit from the use of system testing tools. A systems solution to both areas can be the virtual machine concept, which provides multiple software replicas of real computing systems on one real processor. Each virtual machine has a full complement of input/ output devices and provides functions similar to those of a real machine. One system that implements virtual machines is IBM'S Virtual Machine Facility1370 (VM1370).' VMl370 is an operating system that gives multiple users access to a computer by means of keyboard and display terminals for time sharing, system testing, production, and conversion. VMl370 manages the resources of a computer so that every user, local or remote , appears to have a complete replica of a System 370 including inpudoutput (I/o) devices. Each user of VM/370 can select a different operating system, if desired, because different operating I systems can run concurrently in different virtual machines. This paper describes the capabilities of VMl370. For a historical perspective on VMl370 and the virtual machine concept, see References 2,3,4, and 5. One of the objectives of this paper and those that follow in this issue is to show how VMl370 has provided an architectural base for production as well as experimentation for a wide variety of users and installations. Copying is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first page. The title and abstract may be used without further permission in computer-based and other information-service systems. Permission to republish other excerpts should be obtained from the Editor.