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)
Received: from KL.SRI.COM by LBL.Gov with INTERNET ; Fri, 27 May 88 02:06:59 PDT Received: from CORNELLC.CCS.CORNELL.EDU by KL.SRI.COM with TCP; Wed 25 May 88 12:05:54-PDT Received: from INDYVAX.BITNET by CORNELLC.CCS.CORNELL.EDU ; Wed, 25 May 88 15:02:46 EDT 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