AIX on IBM370 machines

[Oleg Kiselev]

In article <13676 at well.UUCP> sebic at well.UUCP (Dave Truckenmiller) writes:
>Does anyone out there know if one could run AIX on a mainframe (IBM370)
>while also running OSes like MVS, CICS, and TSO?  

Yes.  AIX currently runs as a guest on a VM of its own, in no way interfering
with other virtual machines.

>If this is possible
>is it possible for "files" to be shared between the OS partitions
>while they are running?  

Not quite.  Or rather, yes, but there are peculiarities.  From AIX, one can
go into CP mode of the VM and access files and devices strictly via VM.
The access can be interactive or non-interactive.  If the former, the system
behaves as if you were accessing a pure VM.  In the latter case, the output
of the VM command can be piped to a UNIX program on AIX side.

This means that you can't open a file on a CMS disk from your UNIX program
by doing open(), but there is no reason why a driver can not be written to
access a CMS or MVS or TSO disk s a raw device and do file access according
to that OS's idea of a file system layout.

>Also, will AIX work with the existing 3270
>terminals, or does one need to add ASCII terminals for AIX?

Yes, you can use a 3270, but there are problems.  First, there is a problem
with a block mode terminal interacting with an inheretly character stream
system.  Using vi(1) is possible but hardly pleasant.  Some software uses the
full-screen block mode 3270 with some amount of grace (there is a
modification to curses and terminfo and driver support for that mod to allow
full-screen controllable access to the 3270), but there is no editor that
would use all of the features of the 3270 and work around all the deficiencies
of this (in my opinion) brain-damaged terminal

Second, there is a basic flaw in the very concept of VM that presumes that
the guest OS is a single-user, single-process system.  AIX circumvents this
flaw by making AIX site the "single user" and the UNIX system the "single
process" on the virtual machine.  However, AIX is not capable of allowing
more than one console on the VM.  So only one 3270 terminal, the "console"
from which the AIX site was logged in, can be truly "directly" connected to
the site.  Other 3270 terminals would need to be attached to other virtual
machines.  If such "other" VM is running AIX and is on the same TCF cluster,
all file access and resource use is transparent between sites and for all
intents and purposes, you can say that there are multiple 3270s accessing the
system.  If these "other" VMs are not AIX or are in another AIX cluster,
telnet and rlogin would let the 3270 be connected to the site via BSD-style
pseudo terminals (pty).

Of course, if you have at least one PS/2 running AIX/TCF, you can hang some
2 dosen or so terminals on it and do all your access to your 370 AIX through
a "normal" UNIX style ASCII terminal.  

>We do however have a client who
>wants our U*IX product to "run" on his mainframe.  I was just 
>wondering if we could easily port it to AIX.

Most probably yes.  AIX is very close to both System V and 4.3 BSD.  If you
are not doing anything sVr3-like (streams) and have written your code in a
more or less portable way, you should have no problems at all.
-- 
			"No regrets, no apologies"   Ronald Reagan

Oleg Kiselev            ARPA: lcc.oleg at seas.ucla.edu, oleg at gryphon.COM
(213)337-5230           UUCP: [world]!{ucla-se|gryphon}!lcc!oleg