Re: acceptable number of extents?

Interesting things, those extents. I ran across a table last week that had 274 extents and when I did the calculations, 235 was the maximum number. I still do not know how the engine is still running --- must be magic!! I have seen considerable improvement by elimination of extents --- of course, I also "scattered" the data out onto different spindles. Bill Burton wrote: > MDevlin inquires: > > >>our database has over two hundred tables, 9 of them have more than one > >hundred > >>extents and another 35 have over 10. how signifigantly could this impact > >>performance? > > To which Clem replies: > > >you may now be fairly castigated for not looking in TFM "Performance > >Guide", where it can be found in the discussion on extents in > >chapter 4. Let me take this opportunity to brag about Informix's > >documentation, which is *well* worth the time to read. It's the > >best in the business. > > Prior to V7 extent fragmentation was much more important to stay on top of. > These algorithms are more efficient now. So much so that if you are looking > into a performance issue I would start elsewhere. I have consolidated tables > in excess of 180 extents with no measured performance difference. > > You may run out of the ability to add extents. One of Informix's hairiest > formulas covers this. My mind went numb trying to figure this formula once > and I just went ahead and did the consolidation! > > OTOH if you have little else to do run some timings, consolidate, time again > and post your results here. > > As is the case with many other highly technical questions a definitive > answer is not provided in TF Performance Guide (V7.2 home copy). I have five > or six different Online tuning guides and on some questions I can find five > or six completely different answers and on other questions, none. > > Having read through MANY manufactures doc sets I do appreciate Informix's > very good work. The documentation falls apart at the high end though. > > Enjoy, > > Bill -- David Weis Louisville Internet Marketing Services dweis@louisville-i-market.com 1425 South First Street Louisville, KY 40208 USA 502-637-7316 (Voice) 502-636-1553 (FAX)