Re: Logical Logs Size

I don't know the exact reason but when you set the size of logical log files to a large amount you'll get shared memory error but after enlarging your shared memory size,this will work properly. --babak >From: "Billy Wheeler" <billy@west.co.za> >To: mary@anasazi.com (Mary Curtis), informix-list@iiug.org >Date: Thu, 19 Nov 1998 08:16:27 +0200 >Subject: Re: Logical Logs Size > >On 18 Nov 98, at 16:16, Mary Curtis wrote: > >> Forgive me if my question has been discussed recently or repeatedly. >> I haven't been able to read this newsgroup for ages, but would >> appreicate your input as I have a limited amount of time to research >> my questions. Please respond via email if possible, thanks for your >> help .... Mary Curtis (mary@rez.com) >> >> We are running a large OLTP application on a SUN 10000 platform. We >> have DLTs (jutebox like) tape media. In the past we have always run >> continuous logging to tape (DAT tape drives). Continuous logging to >> the DLTs is no longer the preferred method. We plan to run SUN's >> NetBackup utility to backup the Informix logs when a pre-determined >> number are full. >> >> Our experience has been with running small sized logical logs in our >> continuous logging environment in the past (2k to 8k in size). At >> approximately 4k size, our application will fill a log on the system >> we are discussing in as little as 2 minutes and in as long as 30 minutes >> given the varying times of the day and the load. > >I assume you mean 2000 to 8000 KB here. Informix does not allow >logical logs to be less than 200 KB. > >> The jutebox can't keep up with the logs filling in minutes, the >> storage media is meant for less often backups, but to stream a lot of >> information quickly to the tapes. >> >> The primary question, HOW BIG TO MAKE THE LOGICAL LOGS? Our system >> administration group would like to see 50 megabyte logs. That's way >> too much shared memory for me, or is it?? > >I don't think it is. It's important to differentiate between the logical >logs and their buffers. The logical logs exist on disk, the buffers in >shared memory. So you can make your logical logs as big as just >under 2GB a piece, provided you have enough disk space available. > >> I'm looking for experience and recommendations on suggested >"larger" >> sized logs. Please also comment on the following concerns if you can: >> >> - shared memory (allocating to a bundle to large logs?) >> - long transactions (increasing the log sizes, have you decreased >> the long transaction high water marks? We're >> at 50/60 for LTXHWM/LTXEHWM) >> - recovery (as long as checkpoints are in line, are you >> safe? I've been in recovery on a long >> transaction and hence my concern above about >> rolling back forever and a day on a long txn) > >Chances are that you need either more logs and/or bigger logs if >you get a long transaction. > >> - checkpoints (any special considerations? We currently >> checkpoint at 150secs, duration usually 0-3 >> seconds, no complaints) >> - physical log size (any special considerations when increasing >> logical log size?) >> >> Anything else you think of, please share your experience. > >While you're about it, move your logical logs and physical log out of >rootdbs and into separate dbspaces on separate devices, preferably >with separate controllers. > >It's difficult to make informed comments on the other issues without >knowing a lot more about your transactions and data volume. Still, >HTH. >-- >Ciao, > >Billy > >"Give a man a match and he's warm for an hour, set him on fire and he'll be >warm for the rest of his life!" > ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com