Re: Using telnet with USS

On Tue, 17 Sep 2019 at 16:45, John Murray [email protected] wrote:

>
> And given that USS runs in z/OS (much like Windows can run in a Linux VM)
> I assume that z/OS and the preferences file (I’m not sure you understand
> what that is) have some kind of precedence. I will continue reading until I
> find out what the relationships are.
>

[I did earlier point you to where the precedence (for TCP/IP) is described
in detail.]

But first, please call it z/OS UNIX - not USS. USS is an abbreviation for a
VTAM component, but more to the point USS is not UNIX, but rather a subset
of UNIX services. Also the term OMVS is oft misunderstood; it too is not
another word for UNIX. Best to just not use those terms unless you're sure
you mean exactly them.

Second, it is quite incorrect and will mislead your thinking to say that
"USS runs in z/OS (much like Windows can run in a Linux VM)". The way to
think about it is that z/OS *is* UNIX. It is also MVS, i.e. there are two
sets of interfaces to the same underlying operating system. No matter how a
program gets running, it can use any mix of the UNIX or "classic"
interfaces. So you can run a program in a batch job with JCL, written in
just about any language, and it has full access to UNIXy services like
getpid() or fork() or open() or mkdir() or socket() or whatever. It can
open and read/write UNIX files. And by the same token, you can start a
program by typing its name at a shell prompt, and that program can open and
read/write MVS classic datasets, print to a SPOOLed JES subsystem printer,
use VTAM to communicate, run TSO commands, and so on. As certain IBMers
used to say frequently, "There is no wall." There are no "UNIX programs" vs
"MVS programs", other than in a historical sense.

Tony H.