High numbers of buffer waits in OnLine

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