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. > * 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? Well, a third idea would be to cut the checkpoint interval to, say, 120 (2 minutes). I can't see how a read cache rate can be too high. Your current BUFFERS setting of 300MBytes implies a physical memory of 1.5 GBytes, assuming a single database server on your box. Are you sure that your high BUFFERS setting isn't causing general memory shortages (high paging rates, or even swapping) on your box, thus degrading performance? Neil Truby Londis Holdings London, UK