Re: BUFFERS: How high is too high?

Neil Truby wrote: > > I'm running OnLine v7.13 on Solaris 2.4. I have 160M of physical memory > on my SunSparc 20, and have BUFFERS set to 20000 (or 40M). RESIDENT is > set to 1. The cache read rate is great (99.8%), and the write rate is > OK (~92%). Reducing the size of BUFFERS has in the past seen a drop in > the write cache percentage. > > Performance is crap, and I've recently noticed that my scanning rate is > very high. I suspect that some processes are swapping. So, is it > better to have the DBMS optimal and allow server processes to swap (thus > incurring swap I/O), or reduce the performance of the DBMS (thus > icreasing its write I/Os) and free up more memory for server processes? > > Thanks in advance for any comments > Neil Truby > Chase Manhattan Bank > Bournemouth, UK Neil, I suggest you get hold of a copy of "System Performance Tuning" by Loukides (an O'Reilly book, of course). Use sar (or vmstat if that's what you have but I think it will be sar) to monitor virtual memory performance. Be warned that there are two stages in degredation and swapping is the second. If you are seeing page-outs happening with any frequency then you've reached the first stage and are already seeing degredation then you need to do something about physical memory - either cut the BUFFERs or get more memory. If performance is adequate with reduced buffering then that's OK, if not you more RAM is the only answer. BTW don't worry about page ins. That's just the system reading fresh code pages from disk. Ian