Hello Joerg, You obviously don't work in the same areas I do :) Our serves must be synced to a known references constantly.
Windows 2000 on intel hardware does not keep that good time. I notice our SMP Intel SCB2 motherboard systems (dual Pentium 3 1.26Ghz) drift fast about 30ms every 20 minutes. The harder the load on the CPU, the more the drift. The way we deal with it is to set the clock every 20 minutes ... that way the changes are not big enough to foul up log times and so forth. We wrote a custom program that even makes sure the absolute change is never more than 1/4 of a second (250ms), that way big changes are avoided and can be done during reboot cycles. Normally the every 20 minute change keeps things in sync. I have seen other systems drift slow... each motherboard/CPU combination has a different behavior. We have to connect to outside web servers on a 1/2 second (500ms) accuracy for one of our business ventures, so it is not an option to let the clock drift out. Think of it this way: What if you have 10 servers running the same application, logging to a common database, wouldn't it be worse if they all had different times? PC clocks are not the greatest... Yes, you could let the database provide the timestamp, but sometimes you are recording the time from an event that happens before the actual SQL INSERT statement. I know there are hardware solutions to this (better clock chips and driver that references the hardware), but it has just been easier to set the clock in software. Windows and other operating systems I have worked with have agents to automate this. To answer your questions: How do you deal with doubled timed period? That is where sequence number is combined with time period. In our time-critical application, we can still tell what comes first - even if the time stamp shows otherwise (rare). I fully understand the hibernation issue - but I really doubt too many people are hibernating their servers. Adjusting the clock is pretty common practice that I have seen... The time zone change you reference, Windows practically encourages this. A application solution is to use universal time, but still... clock corrections do have to be made based on my experience. Regards, Stephen -----Original Message----- From: Mensing, Joerg [mailto:[EMAIL PROTECTED]] Sent: Wednesday, November 20, 2002 5:24 AM To: 'Stephen Gutknecht (SAPDB)' Cc: [EMAIL PROTECTED] Subject: RE: Problem with hibernate: 7.4 Beta randomly crashing (Windows) Hi, it concerns my that you think about restting time on a server. You can set your clock into the past, while SAPDB is running you, but only using a time daemon in differential mode. As SAP customer you are forced to do so or your R/3 system may crash. SAPDB may survive that, but i would stop it anyhow before i would to reset the time! Why? What about your applications? How do they handle a 'doubled' time period? If your application survives daylight saving time changes without logical problems (if they use local timestamps), it is save but only very small number of applications do really survive daylight saving time without logical problems. If you wildly modify your local time you will confuse any kind of time depending process. Think about make dependency i.e. or cron jobs... ... but the hibernation problem is a differrent thing, since it resets the internal clock register! On NT you will not influence that internal CPU register by setting the wall clock. The register used is only counting the external clock chrystal signal depending on the MHz provided, but has nothing to do with your wall clock. In a good server environment you should try not to play with the time scale. CU jrg > -----Original Message----- > From: Stephen Gutknecht (SAPDB) [mailto:[EMAIL PROTECTED]] > Sent: Dienstag, 19. November 2002 21:24 > To: Mensing, Joerg; [EMAIL PROTECTED] > Subject: RE: Problem with hibernate: 7.4 Beta randomly crashing > (Windows) > > > Humm... > > This concerns me a bit. What happens if the clock is changed > while SAPDB is > running? Is there any chance that a clock correction (fast > clock set back > 20 seconds every 12 hours) could cause problems? > > Stephen > > > -----Original Message----- > From: Mensing, Joerg [mailto:[EMAIL PROTECTED]] > Sent: Monday, November 18, 2002 4:52 AM > To: '[EMAIL PROTECTED]'; [EMAIL PROTECTED] > Cc: Roedling, Raymond > Subject: Problem with hibernate: 7.4 Beta randomly crashing (Windows) > > > Hi, > with turning hibernation on, Raymond was able to reproduce > the crash. It > seems to be the hibernate mode then... If hibernation is > turned on, the CPU > timer register seems to be spontanously resetted during wakeup. This > confuses time measurement function, which does not expect to > have entered > the dispatcher function after leaving it... > > This does not have an effect both on 'PERFCNTR' and 'TICKS' setting of > HIRES_TIMER_TYPE. So if you decide to allow hibernation of your laptop > you definitly have to modify the parameter. > > CU > jrg > > > > -----Original Message----- > > From: Mensing, Joerg > > Sent: Montag, 18. November 2002 09:34 > > To: '[EMAIL PROTECTED]'; [EMAIL PROTECTED] > > Cc: Roedling, Raymond > > Subject: RE: 7.4 Beta randomly crashing (Windows) > > > > > > Hi, > > in 7.4 a new high resolution timing code is used. The method is > > selectable by parameter "HIRES_TIMER_TYPE" (NT only). Default is > > 'CPU' which means the code uses the RDTSC instruction to get the > > actual tick count from an internal CPU register. > > It seems that this code does not work with your laptop CPU. > > You should try to set the parameter "HIRES_TIMER_TYPE" to 'PERFCNTR' > > or 'TICKS' instead. I hope your random crashes will disappear. > > CU > > jrg > > > > > -----Original Message----- > > > From: Ray Harrison [mailto:[EMAIL PROTECTED]] > > > Sent: Samstag, 16. November 2002 00:20 > > > To: [EMAIL PROTECTED] > > > Subject: 7.4 Beta randomly crashing (Windows) > > > > > > > > > Hello - > > > I have downloaded the beta for 7.4 and have it installed on my > > > laptop - PIII/500mz 384mb ram, Win2K professional, SP3. I'm not > > > really doing anything with it except for the odd table creation, > > > etc. Anyway, I have noticed that at random times, I will get > > > a message about the kernal aborting > > > and shutting down. I have enclosed the error file from > > > today's sessions. I also notice the same > > > thing on my Proliant 6500 - Win 2K Server, 1.5 gig, but have > > > been using the laptop mostly. It may > > > that I am not setting everything up correctly of course, but > > > I assumed that random crashes > > > (seemingly) aren't a good thing! > > > > > > Enclosed, please find the error file and let me know should I need > > > to provide additional information. > > > > > > Warm Regards - > > > Ray Harrison > > > > > > > > > > > > > > > > > > > > > > > > __________________________________________________ > > > Do you Yahoo!? > > > Yahoo! Web Hosting - Let the expert host your site > > > http://webhosting.yahoo.com > > > > > _______________________________________________ > > sapdb.general mailing list > > [EMAIL PROTECTED] > > http://listserv.sap.com/mailman/listinfo/sapdb.general > > > _______________________________________________ > sapdb.general mailing list > [EMAIL PROTECTED] > http://listserv.sap.com/mailman/listinfo/sapdb.general > _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
