[comp.os.vms] Why have a watcher?

IJAH400@INDYVAX.BITNET (05/26/88)

Ralph Becker-Szendy (RALPH%UHHEPG.BITNET@CUNYVM.CUNY.EDU) asks:

< wizards: What resources are tied up by an "idle" user process ?

Answer: You are right, they don't tie up much of the machine, but
resources may include other things: terminal server ports, dial-up
modems, etc.  These may or may not be "scarce" resources at your site.

< Question: Am I right or am I wrong ? If if I'm right, what is the point
< in having a program to forcibly terminat idle processes ??

There are basically two reasons: (1) the use of resources (server ports,
dial-in modems, etc.) mentioned above, and (2) security, e.g., some system
managers don't like the idea of users walking away and leaving their
terminals unattended for long periods of time.

Our site is a rather large university.  We use a "watcher" program
for reason (1) because we only have a limited number of dial-up lines.
At the end of the semester these tend to be busy all the time.
Students will hold them for a long time with idle jobs if we didn't
kill off the idle jobs.  (2) is another reason, some students tend to do
unpleasant things to other user's files when they find a job logged in on
a terminal they want to use.

Of course, there are disadvantages to using a "watcher" also.  Your watcher
should look for CPU time consumed as well as terminal activity.  We used
to simply use a timeout feature in our terminal switch, but it drove
faculty and researchers to complain because some of their jobs tend to
do a lot of disk I/O and use CPU, but do virtually no terminal I/O.
This led to a policy change, now each machine is responsible for it's
own "watching" (or whether to do it at all).  On VMS we use WATCHDOG (from
the DECUS tapes).  Also, installing a "watcher" will cause some users
to immediately sit down and write their own anti-watcher program.  The
trouble with this is that the naive user will tend to write something
like (yes, I've seen people running these):

      PROGRAM ANTIDOG
   10 TYPE *,'Don''t touch this terminal...'
      GOTO 10
      END

Trying to find one of these and kill it off can be quite painful, because
the system might be rather bogged down when you are looking for it, and
if you miss and kill off Prof. Whosit's cruncher, he's going to be p-o'ed.

It would be nicer if the watcher just detached the job, rather than killing
it off completely right then and there.  I believe there is a time-out
feature for virtual terminals, but I don't know if WATCHDOG will detach
rather than kill jobs (and we haven't gotten into virtual terminals here
yet, we are still finishing up the TOPS-20 to VMS conversion).

So, it seems, like most aspects of system management, you have to evaluate
the advantages and disadvantages, and decide whether the use of a "watcher"
is appropriate for your site.  If you don't have any scarce terminal-related
resources that will be tied up by idle jobs, and the security issue is not
a problem, than the only reason I could see to do it anyway would be
because of a facist system management that insists on doing it anyway...

Good luck, and I hope this helps...

        - Jim Harvey            IJAH400@INDYVAX.BITNET

IJAH400%INDYVAX.BITNET%CORNELLC.CCS.CORNELL.EDU%KL.SRI.COM%lbl%sfsu1.hepnet@LBL.GOV (05/28/88)

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Date:     Wed, 25 May 88 12:02 EST
From:     <IJAH400%INDYVAX.BITNET@CORNELLC.CCS.CORNELL.EDU>
Subject:  Re: Why have a watcher?
To:       INFO-VAX@KL.SRI.COM
X-Original-To:  INFO-VAX@KL.SRI.COM
 
 
Ralph Becker-Szendy (RALPH%UHHEPG.BITNET@CUNYVM.CUNY.EDU) asks:
 
< wizards: What resources are tied up by an "idle" user process ?
 
Answer: You are right, they don't tie up much of the machine, but
resources may include other things: terminal server ports, dial-up
modems, etc.  These may or may not be "scarce" resources at your site.
 
< Question: Am I right or am I wrong ? If if I'm right, what is the point
< in having a program to forcibly terminat idle processes ??
 
There are basically two reasons: (1) the use of resources (server ports,
dial-in modems, etc.) mentioned above, and (2) security, e.g., some system
managers don't like the idea of users walking away and leaving their
terminals unattended for long periods of time.
 
Our site is a rather large university.  We use a "watcher" program
for reason (1) because we only have a limited number of dial-up lines.
At the end of the semester these tend to be busy all the time.
Students will hold them for a long time with idle jobs if we didn't
kill off the idle jobs.  (2) is another reason, some students tend to do
unpleasant things to other user's files when they find a job logged in on
a terminal they want to use.
 
Of course, there are disadvantages to using a "watcher" also.  Your watcher
should look for CPU time consumed as well as terminal activity.  We used
to simply use a timeout feature in our terminal switch, but it drove
faculty and researchers to complain because some of their jobs tend to
do a lot of disk I/O and use CPU, but do virtually no terminal I/O.
This led to a policy change, now each machine is responsible for it's
own "watching" (or whether to do it at all).  On VMS we use WATCHDOG (from
the DECUS tapes).  Also, installing a "watcher" will cause some users
to immediately sit down and write their own anti-watcher program.  The
trouble with this is that the naive user will tend to write something
like (yes, I've seen people running these):
 
      PROGRAM ANTIDOG
   10 TYPE *,'Don''t touch this terminal...'
      GOTO 10
      END
 
Trying to find one of these and kill it off can be quite painful, because
the system might be rather bogged down when you are looking for it, and
if you miss and kill off Prof. Whosit's cruncher, he's going to be p-o'ed.
 
It would be nicer if the watcher just detached the job, rather than killing
it off completely right then and there.  I believe there is a time-out
feature for virtual terminals, but I don't know if WATCHDOG will detach
rather than kill jobs (and we haven't gotten into virtual terminals here
yet, we are still finishing up the TOPS-20 to VMS conversion).
 
So, it seems, like most aspects of system management, you have to evaluate
the advantages and disadvantages, and decide whether the use of a "watcher"
is appropriate for your site.  If you don't have any scarce terminal-related
resources that will be tied up by idle jobs, and the security issue is not
a problem, than the only reason I could see to do it anyway would be
because of a facist system management that insists on doing it anyway...
 
Good luck, and I hope this helps...
 
        - Jim Harvey            IJAH400@INDYVAX.BITNET