Re: High numbers of buffer waits in OnLine

David Williams (djw@smooth1.demon.co.uk) wrote: : In article <DtpnBz.3HC@cix.compulink.co.uk>, "\\"Andy Kent\\"" : <akent@cix.compulink.co.uk> writes : >Client is noticing large numbers of buffer waits sometimes cropping up : >while running a *single* heavyweight job under OnLine 5.04. They've got : >plenty of data buffers (12,000) and are getting read caching of 98% and : >write caching usually over 90%. LRU parameters are at the defaults - I've : >suggested they lower LRU_MAX_DIRTY and LRU_MIN_DIRTY to 30 and 20 to keep : >pages cleaner for longer and also possibly LRUs to 4 so it can locate : >clean pages more quickly. : > : >Any comments on this or further ideas of things to try? : > : >They've got 4 chunks on 4 disks with 4 page cleaners. : > : >akent@cix.compulink.co.uk (Andy Kent) : >------------------------------------------------ : >Redland, Bristol, England : If you are getting many bugger waits then increase the number of : buffers. Ignore the caching percentages, just add more buffers. : PS This worked for me. : -- : David Williams Buffer wait means that process is waiting for the buffer used by some other process. Process is waiting because it needs to work with the particular page stored in this buffer. It is similar to lock wait - concurrency problem. So I think increasing the number of buffers will not help. Try to check application logic or data model, if it is a real problem for your client. Regards -- Miroslav Lorenc Software Applications and Systems E-mail: Miroslav.Lorenc@sasprg.cz Prague Czech Republic