Re: When does bufwaits get incremented ?

tony edwards wrote: > > Hey, > I've been trying to track down some information about when bufwaits is > incremented. I found the following in the ODS Admin guide... If after a limited number of attempts to find an unlocked queue, no free buffer has been found the thread will spin wait/sleep on the last queue touched waiting for that particular queue to unlock. This is a bufwait. BTW I found a problem with the random hash used to select the next queue. If LRU==64 the number of bufwaits increases by several orders of magnitude ober performance with either 32 LRUs or 128 LRUs. I do not know if this is a single or multi-peaked function or a smooth curve centered at or near 64. I reported this to Informix last year and found my own workaround (change LRU!=64) in 7.13. I do not know if this is fixed on 7.2x so. In general if BUFWAITS is too large (compare to pagreads + pagwrits from onstat -p bufwaits s/b less than a 1 or 2 percentage points of the total,one of our engines has 671000 bufwaits vs (416100000 pagreads + 12015000 pagwrits) or about 0.0033%); increase the number of LRUs or number of buffers. Art S. Kagel