Re: Bufwaits and Foreground Writes

Like you and Vardan, I've seen this happen on several *XK ports (excluding HP...), and there is no other evidence that a FG write is really happening. I think it is something peculiar to that port. If you aren't seeing evidence of problems, I wouldn't spend too much time on it. Informix is supposedly investigating. Greg "Bernstein, Rick" wrote: > 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.