Re: High numbers of buffer waits in OnLine

In article <31DA19B7.4A6F@west.co.za>, Mark D Stock <marks@west.co.za> writes >David Williams wrote: ><SNIPedySNIP> >> First apologies for the typo above - f and g are next to one another >> on the keyboard! >> >> Buffer wait does mean that the process is waiting for a buffer which >> is in use by another process. However they do not have to be accessing >> the same data. What if you want to read in a page from disk and all >> the buffers are already in use? i.e. the page is not already in the >> buffers but all the buffers are in use so you have to wait for a >> buffer to become free. > >This would show up as foreground writes. Which are VERY undesirable! > No if processes are use the buffers to read you cannot free the buffer until the process has read the buffer it requested. >> This was one of the few questions I raised when I went on the OnLine >> Performance Tuning course last June. > The Informix person whjo gave the course checked with the guys the States who had access to the source code to OnLine. When I increased the number of buffers on a clients machine which had many buffer waits ( it was a 10 CPU Pyramid machine with 128 users, 512Mb RAM / 10 Gb disk) this gave a noticable increase in the performance. >Did they mention that 'bugger waits' (sic) was when you are waiting for users to >stop hogging resources? :^) > >Cheers, ! -- David Williams