Re: Reducing checkpoint intervals...

Narkinsky, Pat wrote: > I run a very busy OLTP system. Currently, checkpoints are taking between 10 > and 20 seconds, and are happening every 5 minutes (as the result of the > checkpoint interval being hit.). > > For obvious reasons, I would like to reduce this. Currently, I see a couple > of things to try: > * Reduce LRU_MAXDIRTY/LRU_MINDIRTY from their current values of 4/2 to > something even lower. (My idea.) I'm leaning towards 1/0 at the moment. Sounds reasonable. > * My application vendor suggest that I reduce the number of BUFFERS to > 50000, thereby having less memory out there, forcing my buffers to become > dirty sonner and thereby be cleaned more frequently, etc... His stated > reason for this is that my read cache hit rate is too high. > Which of these alternatives would you consider more reasonable? Why? > Anyone have a third idea? To me, reducing the number of buffers to get > faster checkpoints seems vaguely silly. But, I've Been Wrong Before. (TM) I think that your vendor needs to take a sys-admin class. I don't think that I've ever heard anyone in an OLTP environment complain that their read cache was too high! But, even if it somehow were, it wouldn't cause long checkpoints. > > -- Vic Goldberg Manager, DBA Team, Acting Manager, Technical Integration Cornell University (607) 254-7441 (Voice) (607) 255-6982 (Fax)