IBM MVT 21.8F Distributions for Hercules

What's MVT?

MVT is a beautiful operating system. Extremely reliable and a great way to learn and understand the modern day successor (or grand-grand-grandchild), z/OS. 

When IBM announced the System/360 mainframe line in April 1964, the plan was to provide just one operating system for batch-oriented use, known simply as the System/360 Operating System (less formally as OS/360, or OS). OS was big, complex and ambitious for its day, and the resulting system was late, buggy and resource-intensive. Installations that couldn't wait, or couldn't afford the hardware required to run OS, opted for one of the smaller, simpler systems that IBM created as alternatives: BOS/360, TOS/360, DOS/360. Eventually, with most of the bugs shaken out OS/360 became IBM's flagship System/360 operating system.

By the time of the final OS/360 release in 1974, system programmers building an OS system had the choice of two control programs: MFT, Multiprogramming with a Fixed number of partition Tasks, and MVT, Multiprogramming with a Variable number of region Tasks. (A third control program option, PCP, Primary Control Program, had been discontinued. PCP could only run one job at a time, which wasted expensive mainframe hardware resouces. Any machine not big enough to run MFT or MVT generally ran DOS/360 instead.)

MVT offered more flexibility and power than MFT, but the price of MVT's advantages was a higher main storage requirement. Because main storage was probably the single most expensive component of System/360 hardware, adding storage was not trivial, and smaller OS shops made do with MFT.

While MVT provided more capabilities than other System/360 operating system alternatives, it was not complete, and add-on products were developed to fill in the gaps. Many users replaced the primitive spool functionality provided natively by MVT with HASP. A few very large installations used ASP to provide not only spooling but loosely coupled multiprocessing and workload management.

Some big mainframe sites continued to use MVT until 1982. 

MVT Distributions

There are two MVT distributions which are quite feature complete, ie inclusive compilers and pre-genned TSO and TCAM. 

One is the MVT 21.8 distribution by Kevin Leonard, which I love because it has both HASP (the  predecessor of JES2) as well as ASP (the predecessor of JES3) both installed and working. 

Release 21.8, the final version of OS/360, survives on the Web in several places. Virtual tapes containing the vanilla IBM 2311 OS/360 distribution are available here.  Also, the complete MVT 21.8F distribution byilt by Kevin  Leonard is here. It has both ASP and HASP installed. 

This MVT package has an excellent readme file which you will need to get MVT up and running with either ASP or HASP. The compilers installed are Cobol, PL/I and of course assembler F. 

The other distribution, which I highly recommend is Juergen Winkelmann's amazing APL\360 distribution. It is primarily an APL-focussed distribution of MVT. However, once you get it up and running you can use as a normal MVT system. It has some compilers installed, such as PL/I, Cobol, Fortran H and Assembler, as well as some CBT goodies like PDS inside TSO. 

You can get Juergen Winkelmann's MVT distro here