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From: taylor@glasgow.glasgow.UUCP (Jem Taylor)
Newsgroups: net.followup
Subject: Re: FYI: VM systems on the net
Message-ID: <653@glasgow.glasgow.UUCP>
Date: Mon, 21-Jul-86 14:09:40 EDT
Article-I.D.: glasgow.653
Posted: Mon Jul 21 14:09:40 1986
Date-Received: Wed, 23-Jul-86 07:29:50 EDT
References: <6340MW9@PSUVM> <-121460420@sysvis> <455@valid.UUCP>
Reply-To: taylor@glasgow.UUCP (Jem Taylor)
Organization: Comp Sci Dept, Glasgow Univ, Scotland
Lines: 43

In article <455@valid.UUCP> gelfand@valid.UUCP writes:
>As to the 'OS' label, VM is more than an operating system. When a user
>logs on under VM, rather than just being a process each user thinks 
>he has his own 370 complete with control registers, general registers,
>PSW, memory and I/O devices as allocated in the directory. Thus you
>have your own Virtual MACHINE - hence the name VM. In this machine
>you IPL (boot) whatever operating system (OS) you want (and have
>access to) e.g. CMS, MVS, DOS/VSE, UNIX. You don't like these?
>There is a good assembler with CMS; write your own. The advantages of this
>system are obvious. If a program in one virtual MAchine does something
>that would crash the machine, only that virtual machine goes down. The
>other users continue to operate. 
>Since VM handles all the I/O, it is an excellent system for people who
>who are debugging Physical IOCS. Vm will not let the user move the 
>disk heads outside their alloted area even with PIOCS. Thus one user
>cannot corrupt anothers files by accident  or even on purpose.

During my undergraduate days, our site's 370/165, running Phoenix/MVT,
had a hardware upgrade to a 3081. To allow system development under MVS,
to bring Phoenix3/MVS up to the standards we were used to :-), without
disrupting the users, the new machine ran VM which provided a virtual 370
to run MVT, and several virtual 3081's to run test, development, and release
versions of Phoenix on MVS. Some 80 concurrent users used the "370", and
I was lucky enough ( as an undergraduate ) to be allowed an ID on the
pre-release "3081" ... using a pseudo-cardpunch/cardreader to move my files
onto the 3081's filestore from the 370's, if I remember right. At the time,
some 10 people might be found at peaktime on that 3081; eventually all the
users migrated to this virtual machine and the disks were re-allocated to it,
with the virtual 370 being withdrawn from service. When I last logged on,
that virtual 3081's concurrent session limit was 200, with >100 logged on
at the time.

VM was described to me as a 'hypervisor', which sounds appropriate. I
assume this is the same 'VM' ?

-Jem.

Give me a VAX I can run BSD Unix _and_ VMS on ... sorry, I forgot. VAXes
are super-minis, not mainframes :-).

-- 
JANET:  taylor@uk.ac.glasgow.cs              -o        Jemima
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