On-disk VMS diagnostics for UNIX (we did it and lived)

[Corot Reason]

We have developed a way to allow either 4.2 or VMS to run on VAXes with
only winchester-type disks. 4.2 is the primary user of the disks, with VMS
consuming only enough space to be minimally useable (no flames, please).
The point of this is to allow DEC to run VMS user mode
diagnostics (or UETP) or whatever to verify hardware problems. We saw this
as a way to avoid some of the problems we have had in the past with 4.2
being a suspect in flakey machine behaviour. The two file systems do not
interfere with each other at all and no modifications of any type were
required to either operating system.
 The conditions under which this setup is seen to be useful and possible are:
	-a two or more disk VAX with no mountable disks.
	-no unix file system on two disks. That is: two scratch disks.
	-the presence of a tape drive that VMS standalone backup can use
		(one of the disks must also have this property)
	-licenses for both VMS and UNIX. (The condition of a VMS license
		might be dropped by the local DEC office as long as DEC
		is the only user of VMS on the machine.)
 On our two-disk VAXes this co-residence of VMS and UNIX on one of the two
disks allows VMS to be booted directly from disk at the cost of an alternate
UNIX root on that disk. UNIX boots off the other disk for normal production.
VMS consumes about 15k sectors on the disk (including about 2k free disk
sectors for VMS to use when it is running).

If there is enough interest in how this is accomplished (it is not difficult,
but does require some knowledge of VMS) I will post instructions
to this newsgroup. Please reply by mail.
	Corot Reason, University of Toronto Computer Services.
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