Talk:VM (operating system)

Article name
I guess this should be at "VM {operating system)"; I'll move it when I get a chance. Noel (talk) 11:39, 24 Nov 2004 (UTC)

Is it just me, or does this article seem very strongly biased?
 * It's not just you. Admittedly I work for a competitor, but this reads like marketing literature.  --192.18.42.249 23:04, 2 May 2006 (UTC)
 * Agreed. I'm mildly surprised this one hasn't gotten an NPOV complaint. In any event, the merge seems like a Good Idea. Jay Maynard 16:11, 9 May 2006 (UTC)
 * I'll raise the NPoV issue --- this article is replete with gushing.
 * Changing this to the more specific tag. --dreish~talk 20:40, 17 August 2006 (UTC)

Does "VM/390" exist? I thought VM/ESA was the initial S/390 VM offering. TimP 03:38, 13 January 2006 (UTC)


 * No. The term VM/390 is one of a dozen terms devised by someone who didn't know the nomenclature and took a wild stab in the dark. What existed were


 * CP-40 Not released to customers.
 * CP-67 Informally, CP/CMS
 * Virtual Machine Facility/370
 * VM/SE Informally, SEPP.
 * VM/BSE Informally, BSEPP.
 * VM/SP
 * VM/SP HPO
 * VM/XA MA
 * VM/XA SF
 * VM/XA SP
 * VM/ESA
 * z/VM


 * SEPP and BSEPP installed on top of the free base; somewhere along the line the free base disappeared and the program product versions were self contained. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:48, 21 September 2010 (UTC)

The VM nomenclenture has never been very tidy - VM/XA, VM/HPO and VM/SP have also been official names.

Both this article and the VM/CMS one are pretty sad. Henry Troup 19:38, 20 September 2006 (UTC)

Some thoughts from a z/VM sysprog
Well, after all the advertising, some thoughts from a z/VM sysprog...

After some time of getting used to it z/VM is a great system to work on. But, of course, it also has its disadvantages.

On the downside, z/VM can be a real pain for the sysprog staff. Many things have to be done manually, especially when upgrading the z/VM environment to a new release which includes tedious editing sessions merging the old system files with the new ones. IBM doesn't offer a simple procedure for this task, while system maintenance can usually be done with a simple command, SERVICE.

Luckily z/VM features REXX, a great scripting language which is nowadays available for almost any system platform, helping to automate the upgrade process. Still, since z/VM had'nt been too popular before Linux for z/Series came to existance, there's a serious lack in support and education personnel - any sysprog dealing with z/VM knows most of the IBM people working on z/VM personally. While these guys do a great job supporting customers, IBM would be well advised to recrute new experts in the near future.

What's more: if a customer doesn't stick to the IBM way of doing things (like running only a few z/VM LPARS) it shows an obvious lack of systems management functionality, at least 'out of the box'. There are many inofficial (aka unsupported) tools available from IBM's z/VM website, but their evaluation and installation is completely up to the customer, and you still find yourself coding many small helper utilities, because the things you need are simply non-existant.

Of course, all of this is absolutely transparent to the system images you run on z/VM, but it can occupy the z/VM sysprog quite a bit. Admittedly, it's fun to code on z/VM, but it can be hard to explain this to someone's boss, who has been told (probably by some IBM consultant?) that z/VM can be run absolutely stable (which is true, at least most of the time) and without much effort (which, in my experience, really depends on the given situation).

Compared to PC-based solutions, z/VM is much more powerful, but at the same time, much more complex to maintain. —Preceding unsigned comment added by 84.59.38.230 (talk • contribs) 19:52, 3 November 2006

Moved from the article to here by RossPatterson 01:07, 4 November 2006 (UTC).

Restructuring of VM and CP/CMS material
I have just finished a reshuffling/rewriting of material from VM and CP/CMS articles. I have tried to incorporate the various comments applicable to this page, though of course there were many issues involved. If you don't see something that you feel was important, naturally please go ahead and make changes. Trevor Hanson 19:39, 3 December 2006 (UTC)

Also: If anybody can upload a public-domain VM teddy bear for inclusion here, that would be nice. I see plenty of bears on the web, but obviously they do not belong to me. I think this would be a nice addition. (In contrast, I did not feel that the huge VM/370 welcome screen from earlier did much for the page.) Trevor Hanson 19:39, 3 December 2006 (UTC)

AIX/Linux under VM
I had stated that VM was required for AIX and Linux, but this was just challenged. After some further investigation, I see that I was misinformed. I had been relying on some strong and credible statements to that effect (which of course I can't put my finger on at the moment), but I now see from other sources that this must have been bogus. IBM's installation docs clearly describe native configurations, e.g. http://www.redbooks.ibm.com/abstracts/sg246264.html. There probably have been specific environments or situations where VM was the only way to go, which led to the claims in the sources I had trusted. I agree that the blanket statements here needed to disappear. I have thus removed the remaining claims about VM being necessary. It would be helpful if some good references about native AIX/Linux configurations could be located, particularly from an historical perspective about AIX. Trevor Hanson 18:55, 17 December 2006 (UTC)

Dates missing
I am not competent to contribute here, but I wish to point out there are too little dates (years), in this article, so that the timeline of the whole VM story is blurry. Even the "History" section only has one year: 1972. You can't figure out what happened later and when. If the experts could fix this, I'd be very grateful. —The preceding unsigned comment was added by Special:Contributions/ (talk)
 * Good point. I had been hoping that a current z/VM expert would step in on this page and add some more detail about recent history. I have added the z/VM original release date (October 2000) and a link to IBM's z/VM release history. Plenty of early dates are found in the CP/CMS articles. Details on the middle years between 1972 and 2000 could be beefed up by somebody with the expertise and interest. Most of the release dates should be close to the associated hardware announcements, e.g. the XA versions were linked with the release of XA hardware. On the other hand, there probably aren't too many people who care about specifics on those events. The IBM archives remain the best bet for a timeline of versions. Trevor Hanson 22:34, 22 August 2007 (UTC)

Restructure of articles about IBM mainframe operating systems
After a big edit of MVS I concluded that the whole set of articles about IBM mainframe operating systems from System/360 onwards needed to be re-structured to minimise overlap and to make clearer the evolutionary relationships between these operating systems (notably in memory management, which is historically a major distinguishing feature). There is already some support for this proposal. Please add comments at Talk: MVS. Philcha 23:56, 20 October 2007 (UTC)

Image copyright problem with Image:ZVMCMS.png
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 * That there is a non-free use rationale on the image's description page for the use in this article.
 * That this article is linked to from the image description page.

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He's dead, Jim - AIX
The S/370 versions of AIX have been dead for well over a decade; essentially, since the availability of a Unix environment in MVS/ESA SP Version 4. Linux on z, of course, is alive and well.Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:48, 21 September 2010 (UTC)

Actually it was stillborn. One licence was sold. — Preceding unsigned comment added by 80.198.50.213 (talk) 03:04, 2 November 2014 (UTC)

Provenance of term Hypervisor
The term Hypervisor did not come in with VM; it was used in the 1960's. I don't recall whether it was used in the context of CP-67 or in a different context. Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:51, 16 February 2011 (UTC)


 * And what, pray tell, is your reference? With respect to VM/370 and its successors, the term Hypervisor was coined by me in late 1971 or early 1972, while we were reorganizing and rewriting the Control Program functions.  At the time, source module names and external symbols were limited to 8 characters.  IBM internal standards required that the first three letters were the assigned Component Code; the next three characters were a module identifier, and the last two were reserved for entry point identification.  The component code for VM/370-CP was 'DMK' and the code for VM/370-CMS was 'DMS'.  John Seymour was responsible for the CP program interrupts handler, DMKPRG; page faults came in there, and he was also the author of DMKPAG.  I was responsible for the privileged operation exception handler, DMKPRV.  One of the privileged operations handled by DMKPRV was the Diagnose instruction, which CP-67/CMS and VM/370 used for "paravirtualized" requests from the guest system to the virtual machine monitor - i.e. to the Hypervisor.  I named and wrote DMKHVC, the Hypervisor Call module, derived from the S/360 Supervisor Call instruction (SVC).  [I cannot avoid violating the 'No Original Research' constraints of Wikipedia, for reasons that should be obvious.]  If you look around online, you should be able to find "The Origin of the VM/370 Time Sharing System" by R. J. (Bob) Creasy, IBM Journal of Research & Development, Vol. 25 No. 5, September 1981, and/or one or another version of Melinda Varian's "VM and the VM Community, Past, Present, and Future" from 1989 through the 1990's. Dave Tuttle (talk) 23:19, 24 February 2011 (UTC)


 * And what, pray tell, is wrong with the reference in Hypervisor?


 * I don't know when work started on CP-40, but RPQ E880801 was well before Virtual Machine Facility/370. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:41, 27 February 2011 (UTC)


 * I have been wrong before; no doubt it will happen again. I personally worked at MIT with a S/360-65 that had the IBM 7094 emulator microcode option, in late 1967 or early 1968.  The "shared memory" in that case was actually the processor microcode, not main memory.  The MIT Computation Center installed a S/360-40 in the same room as the (upgraded) S/360-65 and interconnected them via a Channel-to-Channel Adapter (CTCA).  I worked during the summer of 1967 to modify a copy of IBM's Attached Support Processor (ASP) software, install it on the S/360-40, and set it up to run mixed-mode batch on the S/360-65.  The ASP software on the Model 40 would recognize whether an incoming job (card deck) was an OS/360 job or an IBSYS (7094) job, then switch the main processor between OS/360 and IBSYS as necessary.  I do not recall the use of Hypervisor in that context, but the circumstance does make sense. Dave Tuttle (talk) 16:48, 1 March 2011 (UTC)


 * The ASP support for doing an IPL of the Main processor was not what I and Don Skiba were referinng to, and I've never heard it referred to by the term Hypervisor. RPQ E880801 allowed the emulator and OS/360 to be in memory concurrently, and had nothing to do with ASP. Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:56, 7 March 2011 (UTC)


 * I'm being to question the accuracy of this "History". Without a hard link back to RPQ E880801 the 2 citations provided here can't be considered accurate


 * SimonBramfitt (talk) 19:10, 30 January 2013 (UTC)

Examples of (deeply) nested virtualization?
The paragraph about running VM inside VM mentions "The litterature" providing practical examples of nested virtualization "five levels deep". I'm curious to know which litterature that is so that I can find out what the examples were. 88.131.66.80 (talk) 16:13, 19 October 2011 (UTC)

If you look at page 55 of the document "VM and the VM Community" that is already referenced you'll find the following paragraph at the bottom:

<<The System/370 relocation architecture was different from the 360/67 architecture; it allowed both 2K and 4K pages and both 64K and 1M segments. So, Auroux modified his modified CP-67 to support 64K segments and the new System/370 instructions. He ran that system second-level, so he could run a virtual S/370 third-level. He developed a prototype “CP-370” in that third-level virtual machine. Then, to test this CP-370’s virtualization of System/370 virtual memory, he had to run it both third- and fourth-level, with a couple of CMS machines running fifth-level.>> — Preceding unsigned comment added by Deasington (talk • contribs) 11:58, 12 July 2012 (UTC)

VM - the missing bits!
In the late 1980's we did some interesting work running CICS directly on VM and also under VM/CMS and VM/PC. VM/PC doesn't seem to get a mention anywhere although it was a full VM implementation running on 370 order code on the XT or AT/370 hardware. There were also communications facilities between VM/PC and a host running either VM/CMS or CICS using a DIAG '78' (from memory...) interface. Does anyone remember more, or have documentation? — Preceding unsigned comment added by Deasington (talk • contribs) 15:26, 10 July 2012 (UTC)

Closed source?
One thing that made VM unique among IBM's operating systems was that it was open source, not in the sense of "free" but in the sense that the source code was provided with the OS, users could modify it, and mods were available that people openly shared. Beginning in the 1980s, components started coming out without source and I have no idea what percentage of source code is provided these days. But is "Closed source" an accurate description? If anything, it was the first major OS in history that wasn't closed source in the traditional sense. 50.0.107.222 (talk) 22:34, 6 May 2014 (UTC)


 * I think the current wording explains this quite nicely:


 * "The early history of VM is described in the article...History of CP/CMS. ... Early releases of VM continued in open source, and today are considered to be in the public domain. This policy ended in the mid '80s, when VM became a 'For-charge Licensed System Product'."


 * Also see: History of CP/CMS. --Guy Macon (talk) 02:51, 7 May 2014 (UTC)
 * VM/BSE (BSEPP) and VM/SE (SEPP) came out before VM/SP, well before the mid 1980's. In fact, the date for VM/SP is 1980/02/11, also before the mid 1980s. Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:59, 27 May 2014 (UTC)


 * History of CP/CMS seems to have been moved to CP/CMS. RossPatterson (talk) 23:24, 27 May 2014 (UTC)


 * IBM did not restrict the source code for any commercial OS in the 1960s, well before VM. For that matter, I'm not aware of any vendor that had a closed source OS in the 1960s. --Shmuel (Seymour J.) Metz Username:Chatul (talk) 13:52, 6 October 2021 (UTC)

External links modified
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 * Added archive https://web.archive.org/20061018022910/http://www.vm.ibm.com/devpages/christin/vmwebart.html to http://www.vm.ibm.com/devpages/christin/vmwebart.html

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FOSS? The free base was, but not anything recent
While Virtual Machine Facility/370 was distributed in source code, IBM instituted a policy of Object Code Only (OCO) for newer, chargeable, software. The FOSS designation would be reasonable for an article on only CP-40, CP-67 and VM/370, but not for an article that covers VM/SP through z/VM. Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:54, 27 March 2019 (UTC)

Should there be a section on PR/SM?
Processor Resource/System Manager (PR/SM) facility on IBM's z line started out as a modified CP on the 3090 using the same SIE instruction as VM/XA MF through z/VM. Should there be a brief description, linking to PR/SM and Logical partition as the main articles? Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:01, 4 September 2019 (UTC)

Privileged instructions
Starting with VM/XA MF, doesn't SIE directly handle the execution of certain privileged instructions, e.g., LPSW? --Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:01, 19 August 2021 (UTC)

Format of OS lists?
The lists of operating systems under VM currently have a bold tag with no line break, directly followed by the text for the OS. Would it be better to have description lists, which also bold the tag but put the text, indented, on a new line? E.g.:
 * Group Control System (GCS)
 * GCS Provides a limited simulation of the MVS API. IBM originally provided GCS in order to run VTAM without a service OS/VS1 virtual machine and VTAM Communications Network Application (VCNA). RSCS V2 also runs under GCS.
 * Remote Spooling Communications Subsystem (RSCS)
 * RSCS provides communication and information transfer facilities between virtual machines and other systems
 * Group Control System (GCS)
 * GCS Provides a limited simulation of the MVS API. IBM originally provided GCS in order to run VTAM without a service OS/VS1 virtual machine and VTAM Communications Network Application (VCNA). RSCS V2 also runs under GCS.


 * Remote Spooling Communications Subsystem (RSCS)
 * RSCS provides communication and information transfer facilities between virtual machines and other systems

Does it seem clearer with that formatting? --Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:37, 6 October 2021 (UTC)

TPF
Can ACP/TPF run under VM? Peter Flass (talk) 15:04, 7 May 2023 (UTC)
 * I thought that I had responded to this, but my update seems to have disappeared. Briefly, CP-67 should be able to run Programmed Airline Reservations System (PARS), VM/370 should be able to run IBM Airline Control Program (ACP), ..., z/VM is able to run z/TPF. I haven't looked lately, but it used to be that the only way to run TPF on multiple processors concurrently was to run multiple copies under VM. -- Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:43, 8 May 2023 (UTC)