RE: Bufwaits and Foreground Writes

Vardan, Thank you for your response. Our experiences seem to parallel yours. Our foreground writes started after an upgrade from IDS 7.30.UC7XB to IDS 7.30.UC7XK. With this latter release we were able to set NOLRUPRIO=1 to avoid tying up most of our buffers with index pages. I have tried many changes without any success: * Increasing CLEANERS and LRUS * Increasing BUFFERS * Reducing read-ahead (RA_THRESHOLD) pages * Increasing LRU_MIN/MAX_DIRTY * Decreasing LRU_MIN/MAX_DIRTY Art Kagel made a couple of other suggestions which I will try next week. Rick -----Original Message----- From: Vardan Aroustamian [mailto:vaar@geocities.com] Sent: Friday, December 31, 1999 1:36 AM To: informix-list@iiug.org Subject: Re: Bufwaits and Foreground Writes In article <84gb3g$sho$1@news.xmission.com>, "Bernstein, Rick" <rbernste@alarismed.com> wrote: > > Despite our tuning efforts, we are encountering a significant number of > bufwaits and foreground writes > on our production SAP system. This system runs IDS 7.30.UC7XK on a 4-way > RS6000 R50 (AIX). I just want to share little bit from my recent experience. We had 0 foreground writes when we was on 7.30UC7XB Foreground writes appeared just after upgrade to 7.30UC7XK. Nothing changed on system - only upgrade. System is 4CPU, Solaris, SAP 4.5B. That number is always increasing. Sometimes during checkpoint, sometimes when engine flushing when % of dirty buffers reaches LRU_MAX_DIRTY. I tried (without success) to catch is it really foreground write or it's just wrong statistics. I believe engine is not performing foreground write at that time, but there isn't proof of that. I contacted SAP and got answer something like: Some of our customers using 7.30.UC7XK also found similar situation with increasing number of foreground writes ... not affecting performance ... you can ignore that value in onstat -F output. I'm writing from home and can not provide exact answer from SAP but meaning is above. Regards Vardan from home vaar@earthlink.net <SNIP> > Thank you for any assistance or insight which you can provide. > > RIck Bernstein > > -- Vardan Aroustamian vaar@geocities.com Sent via Deja.com http://www.deja.com/ Before you buy.