What is MVS?

MVS, which stands for Multiple Virtual Storage, is one of the oldest operating systems developed by IBM and distant relative of what we nowadays call DOS. MVS has its own programming language, JCL (Job Control Language). Four decades after MVS was created (1974), JCL is still heavily used to run applications in mainframes and the technology, in general, remains king although considered by many as obsolete technology.

By the way, there is an old joke in the field where a COBOL program needs to be fixed, but the person who wrote it is dead. This is one reason many large companies like Fortune 100, banks, insurers, telecommunication providers, retailers and airlines prefer not to move away from mainframes and MVS.

This is also a reason why some programmers learn languages like COBOL (the most commonly used) since there is always the possibility that an old program could break. These programmers can make good money on a single job.

Where I work the mainframe is about to be retired later this year in favor of PeopleSoft (Oracle backend) after years of employees complaining that the PeopleSoft system is not as good as the obsolete program used to retrieve data and run reports for almost thirty (30) years — not to mention the seven-figure bill for development. In some way, MVS is a dear technology of mine.

The following table shows the history of MVS as per the book Understanding Operating Systems (ISBN 9780534503536) by Ida Flynn.

Timeline:

  • OS/360 for IBM 360 (1964)
  • OS/MFT (Multiprogramming with Fixed number Tasks) for IBM 360 (1967)
  • OS/MVT (Multiprogramming with Variable number Tasks) for IBM 360 (1968)
  • SVS (Single Virtual Storage)
    OS/VS1 (Virtual Storage 1)
    OS/VS2 (Virtual Storage 2) for IBM 370 (1972)
  • MVS (Multiple VirtualStorage) for IBM 370 (1974)
  • MVS/XA (MVS with Extended Architecture) for IBM 370 (1981)
  • MVS/ESA (MVS with Enterprise System Architecture) for IBM 370 (1985)
  • MVS/ESA (MVS with Enterprise System Architecture for IBM 390 (1990)
  • OS/390 (Open Server 390) for IBM 390 (1996)
  • z/OS 64-bit for zSeries (2000)
  • IBM z/VM for zSeries (2004)

If you would like to test MVS, you can use OpenVMS by HP or FreeVMS in a .VDI.