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

[kemain.nospam at gmail.com]

> -----Original Message-----
> From: Info-vax <info-vax-bounces at rbnsn.com> On Behalf Of Scott Dorsey
> via Info-vax
> Sent: Sunday, November 06, 2022 9:55 AM
> To: info-vax at rbnsn.com
> Cc: Scott Dorsey <kludge at panix.com>
> Subject: Re: [Info-vax] What does VMS get used for, these days?
> 
> 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
> 

One feature in OpenVMS that is not used as much for server resource
management as it might (should?) be is the native class scheduler.

SYSMAN> help class (for more info - can implement by primedays, UIC,
username, account etc.)

Extract from SYSMAN> Help class add
"The class scheduler provides the ability to limit the amount of CPU time
that a system's users receive by placing users in scheduling classes. Each
class is assigned a percentage of the overall system CPU time. As the system
runs, the combined set of users in a class is limited to the percentage of
CPU execution time allocated to their class.

Users might get some additional CPU time if the qualifier /WINDFALL is
enabled for their scheduling class. Enabling the qualifier /WINDFALL allows
the system to give a small amount of CPU time to a scheduling class when the
scheduling class's allotted time has been depleted, but a free CPU is
available."

Regards,

Kerry Main
Kerry dot main at starkgaming dot com




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