Operating System/Virtual Storage 1
, or OS/VS1
was an IBM mainframe
IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...
computer operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
designed to be run on IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...
It was the successor to the Multiprogramming with a Fixed number of Tasks (MFT) option of System/360
The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...
's operating system OS/360
OS/360, officially known as IBM System/360 Operating System, was a batch processing operating system developed by IBM for their then-new System/360 mainframe computer, announced in 1964; it was heavily influenced by the earlier IBSYS/IBJOB and Input/Output Control System packages...
OS/VS1, in comparison to its predecessor, supported virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
(then called virtual storage
OS/VS1 was generally available during the 1970s and 1980s, and it is no longer supported by IBM.
OS/VS1 was OS/360 MFT II with a single virtual address space; by comparison, OS/VS2 SVS
Single Virtual Storage refers to Release 1 of Operating System/Virtual Storage 2 ; it is the successor system to the MVTBut not 65MP option of Operating System/360...
was OS/360 MVT with a single virtual address space. OS/VS1 was often installed on mid-range IBM mainframe systems, such as the System/370 Model 148.
OS/VS1 was intended to manage a medium-sized work load (for the 1970s)
consisting only of batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...
applications, running within a fixed number of operating system partitions via the batch job management system Job Entry Subsystem 1 (JES1).
This was in contrast to OS/VS2 which was intended to handle larger work loads
consisting of batch applications,
online interactive users (using the Time Sharing Option
In computing, Time Sharing Option is an interactive time-sharing environment for IBM mainframe operating systems, including OS/360 MVT, OS/VS2 , MVS, OS/390, and z/OS.- Overview :TSO fulfills a similar purpose to Unix login sessions...
, or TSO),
or a combination of both. However, OS/VS1 could, and often did, support interactive applications and users by running IBM's CICS
Customer Information Control System is a transaction server that runs primarily on IBM mainframe systems under z/OS and z/VSE.CICS is a transaction manager designed for rapid, high-volume online processing. This processing is mostly interactive , but background transactions are possible...
transaction processing monitor as a job within one of its partitions.
Installation and modification of OS/VS1 was accomplished via IBM's cumbersome System Generation
System Generation is a two-stage process for installing or updating OS/360, OS/VS1,OS/VS2 , OS/VS2 and chargeable systems derived from them. There are similar processes for, e.g., DOS/360, which this article does not cover...
OS/VS1 went through seven product releases.
OS/VS1 Release 7 was enhanced by fourth release of the IBM OS/VS1 Basic Programming Extensions (BPE) product.
BPE provided support for new 1980s hardware,
such as 3380 DASD
In mainframe computers and some minicomputers, a direct access storage device, or DASD , is any secondary storage device which has relatively low access time relative to its capacity....
The last OS/VS1 product release,
OS/VS1 Basic Programming Extensions (BPE) Release 4,
was announced by IBM in 1983 for general availability in March 1984
(product 5662-257, announcement letter 283-266, 15 September 1983).
IBM announced the end of functional enhancements to OS/VS1 in 1984. IBM recommended OS/VS1 installations migrate to MVS/370 or MVS/XA.
To assist with the migration to MVS/XA, IBM made the VM/XA Migration Aid.
It allowed installations to run OS/VS1 and MVS/XA simultaneously on the same machine, as guests of a third system - VM/XA. This way, the new MVS/XA system could be tested while the old production OS/VS1 system was still in use.