Re: Number of extents in an instance

In article <6qv8tu$e31$1@nnrp1.dejanews.com>, mdevlin8648@my-dejanews.com wrote: > How many extents are exceptable? with multiple extents how drastically is > performance reduced? our databse consists of around 200 tables, 9 of which > have over 100 extents and about 40 have more than ten. I am very new to > informix and am trying to tune our configuration for better performance. > could these large number of extents be haveing a major performance impact? > Any help would be greatly appreciated. > > -----== Posted via Deja News, The Leader in Internet Discussion ==----- > http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum > Normally, 100 extents are not "good" to have. In general, if you are performing a decision support (dss) type of query, you definately would want to have a lesser number of extents with the optimal being one. This would permit the disk arm to sweep across the platter to read the data as opposed to having the disk arm jump all around to get the data. An indexed access would not feel as much of an impact of a high number of extents since you are accessing the data via a B+tree, but there would be an impact. I would suggest you calculate the size of the data and any associated indexes (if attached) and unload, drop and recreate the high-extent-tables. You will most likely see an improvement in performance. Gary. -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum