VM/370 security and performance

[lcc.barry at UCLA-LOCUS.ARPA]

I've read several interesting criticisms of VM/370 and at least one uninformed
one.  There are  several good points about VM/370:

1) CMS is the nearest thing to a friendly OS IBM has come up with.

2) The entire microfiche for VM/370 (CP, CMS, IPCS, and RSCS) is about 6" thick.
OS/360 took up two card boxes; I assume MVS is even bigger.

3) Maybe some system programmers in u-wiz ENJOY working between 2 and 6 AM
when there's a new version of the system to build, test, and install.  With
VM, you do your work during the day in parallel with production use of your
machine.  When the system works, you come in ONE night to put it in the
production machine and make sure it works there.

4) The layered approach of VM/370 (370 apparency to virtual machines, Op
Sys in vm to present a favorite interface to users) keeps the interfaces
simple while allowing the users to have a powerful operating system.

Much of the simplicity and power of VM/370 comes from something it has in common
with unix: it was built by a few people (~4) for their own convenience and 
somehow got out.

Unfortunately, VM/370 has gotten more complicated with the addition of many
new facilities: 
	For control of virtual consoles: SNA virtual console communication 
service; message system service; single console image; logical device support
(this last is used by PassThru, VM's equivalent of TELNET).
	For communication between virtual machines:  Virtual Machine 
Communications Facility (VMCF) and Inter-User Communication Vehicle (IUCV).
	CMS/DOS is almost as big as the rest of CMS.
	Likewise for CMS VSAM.

In spite of its growing pains, VM/370 & CMS is still the cleanest, easiest to
use operating system for 370-like machines around.  (Unless you can talk
IBM out of VMIX, a unix built on a modified VM/370.)

barry