Re: Why does 5.04 lock up when logs fill?

In reply to tom dorgan's email about Why does 5.04 lock up when logs fil, on 3 Oct 96 Hi Tom, > I guess the subject says it all. the server just quits and you have to > restore the database? This is what our admin people are doing, anyway > and its a 6 hour process and all you get is what you had on your last > backup. Doesnt seem like the last word in data safety/reliability. > > somebody does a transaction which affects quite a few rows of the > database, the logs fill, and everything comes to a very quiet halt. > > tom. Apologies in advance for the length of this article :-) What you are getting into is "Long transaction" situation. Basically what happens is one of your applications starts filling up the logs at a very fast speed. ( Mass updates , deletes , inserts , select into temp etc. ). At a particular point in time i.e. when a particular percent of logical logs is full, the Informix server starts to rollback such a transaction. This percentage is defined in the tbconfig as LTXHWM. If the logical logs fill up past a percentage point called LTXEHWM, ( exclusive high water mark ) then the server stops all other activities except archives and just keeps on rolling back the offending process. However, if the LTXHWM andLTXHEWM are set to very high level, say around 80% and 90% , then there is no way that Informix server can rollback the whole process. This is because rolling back also keeps on filling up the logical logs. At this point in time you can continue to back up logical logs and then when all the logs show UB status , bring down Informix by mode->shutdown command and then do startup. There is a possibility that the server will come up fine. Some of your transactions may, however, have been rollled back. This can be surmised from the turbo.log file. The solution : 1> Decrease LTXHWM and LTXEHWM. Informix recommends that you keep these values at 60% and 70%. 2> Increase the number of logical logs or their sizes. 3> Modify the offending application. I think this is your best option. Look for mass inserts etc More info. on the Long transaction is available in "Informix OnLine admin guide" HTH, Ravi... -- Ravi Joseph Pinto, mailto:ravi@in.dhl.com Consultant, Astra Infotech, Mumbai, India voice :91-22-8503000 extn. 1531 Standard disclaimers apply.