OS/VS1 was generally available during the 1970s and 1980s, and it is no longer supported by IBM.
OS/VS1 was intended to manage a medium-sized work load (for the 1970s) consisting only of batch processing applications. 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, TSO), or a combination of both.
OS/VS1 was OS/MFT with a single virtual address space; OS/VS2 SVS was OS/MVT with a single virtual address space.
OS/VS1 used the batch job management system Job Entry Subsystem 1 (JES1).
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 (disk).
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 Mirgration 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.