OS/VS1

OS/VS1
Company type	Operating system
Industry	Computer software
Predecessor	OS/360 MFT
Founded	1972
Headquarters	Armonk, United States
Products	IBM mainframe operating system
Owner	IBM

Operating System/Virtual Storage 1 (OS/VS1) was an IBM mainframe operating system developed for the IBM System/370 platform. It replaced the Multiprogramming with a Fixed number of Tasks (MFT) feature of OS/360 by incorporating virtual memory capabilities, then referred to as virtual storage. OS/VS1 saw extensive use throughout the 1970s and 1980s but has since been discontinued and is no longer supported by IBM.

Description

Essentially, OS/VS1 represented an evolution of OS/360 MFT II, enhanced to include a single virtual address space. In contrast, OS/VS2 SVS was derived from OS/360 MVT and featured a comparable virtual address space. This operating system was commonly installed on mid-range IBM mainframes such as the System/370 Model 145 and later the Model 148.

OS/VS1 was tailored for medium-scale workloads, predominantly batch processing tasks, operating within a fixed number of partitions controlled by the batch job management system, Job Entry Subsystem 1 (JES1). Unlike OS/VS2, which accommodated larger workloads including both batch and interactive online users through the Time Sharing Option (TSO), OS/VS1 concentrated on batch processing but frequently supported interactive applications via IBM's CICS transaction processing system running as jobs within its partitions.

The installation and configuration of OS/VS1 involved the intricate IBM System Generation (SYSGEN) procedure.

Remote Entry Services (RES)

OS/VS1 provided an updated alternative to the OS/360 Remote Job Entry (RJE) system, allowing job submission and retrieval through terminals such as the 2770, 2780, and 3780, along with workstation software compatible with systems like the IBM 1130. RES incorporated the Remote Terminal Access Method and offered closer integration with job management functions than its predecessor RJE.

IBM upgrades

Throughout its lifecycle, OS/VS1 was released in seven versions. Release 7 received four updates under the OS/VS1 Basic Programming Extensions (BPE), product number 5662-257. These updates introduced support for hardware introduced in the 1980s, including the 3380 Direct Access Storage Device, and enabled VM handshaking capabilities between VTAM and VM/VTAM Communications Network Application (VCNA).

The last BPE update, OS/VS1 Basic Programming Extensions Release 4, was announced in September 1983 with availability scheduled for March 1984. In 1984, IBM announced that no further functional enhancements would be made to OS/VS1 and advised users to transition to MVS/370 or MVS/XA. To facilitate this migration, IBM released the VM/XA Migration Aid, which allowed OS/VS1 and MVS/XA to operate simultaneously as guest systems on a third platform (VM/XA), enabling testing of MVS/XA while continuing production on OS/VS1.

On January 24, 1989, IBM declared that marketing for OS/VS1 and its BPE would end on April 24, 1989, with support services concluding on February 28, 1990.

Time-sharing

Although IBM's Time Sharing Option (TSO) required using VS2, customers running a 370/145 or 370/148 had alternative time-sharing solutions available. One method combined VM/CMS for time-sharing purposes alongside a guest "machine" executing OS/360 MFT II to handle batch jobs.

Conversational Remote Job Entry

CRJE, an optional feature available in OS/360 MFT II, OS/360 MVT, and OS/VS1, allowed users operating line-mode terminals to perform text dataset editing, submit batch jobs, and retrieve job results.

TONE for VS1

TONE, a time-sharing system similar to TSO designed for VS1 and VS ONE, was developed and distributed by Tone Software Co. It provided improvements in managing IBM control blocks.