[Info-vax] What does VMS get used for, these days?

[Scott Dorsey]

Robert Carleton  <rbc at rbcarleton.com> wrote:
>I work in an environment where there's lots of scientific computing on the =
>Linux platform. One of the things about it, is that getting compute time is=
> very competitive, and our users/coders game the batch systems to gain an a=
>dvantage in getting their jobs to run. We can't use the stock Linux batch s=
>ystems (at, batch, atd, cron, and friends) for that work, though the system=
> administrators probably use those for some of what they do. We have to use=
> add-on batch systems for controlling those jobs.

These days it's also very common to have multiple synchronized jobs on
different nodes, so Linux has add-on tools like PBS for dealing with that.
And you get the added benefit of resource management of course.

>I'm not familiar with the VMS batch facilities yet (I'm a Linux/BSD jockey)=
>, but I've heard that they are pretty advanced. Perhaps that would provide =
>an advantage, at least when there is a lot of competition for compute resou=
>rces.

First thing: VMS has heavyweight processes.  There's a lot of stuff in the
process, so spawning off new processes takes a good while, and you don't do
it very often.  Conceptually different than Unix and Unixalikes where the
processes are lightweight and the overhead of a fork is minimal so you fork
off a new process for nearly everything.

Whereas the concept of "resources" in Linux is fairly simple, VMS has a lot
of different resources which are managed statically by the operating system.
Some of that resource management goes into making the processes more
heavyweight.  This can be a powerful tool to keep multiple users from
interfering with one another on a system with limited resources.  In a
scientific computing environment it can also be a pain in the neck because
people will run their job for three days and then hit a working set limit
and need to figure out what the limit really should be.

But yes, some of the "big computer" batch features that you get with PBS and
OS/360 are present by default in VMS, and that's a nice thing.  Using VMS on
a machine acting as a front-end to a high-speed computer was great.

Mind you, the best batch management system in the world won't keep researchers
from paying the second shift operators under the table to move their jobs to 
the front of the queue.
--scott

-- 
"C'est un Nagra. C'est suisse, et tres, tres precis."