Re: Latch Waits

Colin, I assume you are running some 7.3x version? The mutex name you see is truncated and really is "global cache mutex". This is either the mutex protecting the distribution cache (holding update statistics medium and high information) or the one for the stored procedure cache. If you are able to catch a thread that is mutex waiting with "onstat -g stk <tid>" I should be able to tell which one it is. But maybe you can guess anyway. Maybe this is not related to your changes. You should try and set these onconfig parameters higher: for stored procedure cache: PC_POOLSIZE, PC_HASHSIZE onstat -g prc for distribution cache: DS_HASHSIZE, DS_POOLSIZE onstat -g dsc Michael Colin Dawson wrote: > Hi, > > Yesterday I started getting a lot of latch waits - onstat -u had "S" in the > 1st position in the flags column. onstat -g lmx showed a lot of processes > waiting on a mutex called "global cach" I cannot find much information about > this mutex. > > The question I'm asking is why would I get this situation? It has been > running fine previously. I did change BUFFERS from 1900000 to 4000000 and > RESIDENT from -1 to 0. So why would changing these two parameters cause the > mutex waits. When the change was made checkpoints went up from 1-3 seconds > every 15 minutes to 5+ seconds every 5 minutes (leaving the interval at 15 > minutes meant we had checkpoints > 10 seconds) > > Some onconfig parameters: > LRUS 511> CLEANERS 127 (onstat -u shows some page cleaners not doing any work - no of > writes=0) > CKPTINTVL 900 > LRU_MAX_DIRTY 1 > LRU_MIN_DIRTY 0 > RA_THRESHOLD 4 > NOAGE 1 > NETTYPE tlitcp,15,256,NET> > onstat -u shows approx 1300 connections> > Any insight into why I had the above problem would be appreciated. > > > > Many Thanks > > > Colin Dawson > > www.ladbrokes.com > > > sending to informix-list