Re: Number of extents in an instance

Jay Aymond wrote: > > 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 > > I try to keep my extents at 8 or less. It keeps the disk heads from moving as > much when accessing the table. Also, with the 5.x engine, I belive that when > the number of extents exceeded 8, it caused an extra I/O to be done. I'm not > sure if that's true with the 7.x engine. In 5.x only the first 8 extents were tracked in SHM. This is NOT the case in 7.x. However, as everyone has said, keeping table pages contiguous is preferable, which means keeping extents to a minimum. Cheers, -- Mark. +----------------------------------------------------------+-----------+ |Mark D. Stock - Informix SA http://www.informix.com |//////// /| |mailto:mdstock@informix.com http://www.informix.com/idn |///// / //| |http://www.iiug.org +-----------------------------------+//// / ///| | Tel: +27 11 807 0313 |If it's slow, the users complain. |/// / ////| | Fax: +27 11 807 2594 |If it's fast, the users keep quiet.|// / /////| |Cell: +27 83 250 2325 |Therefore, "No news: travels fast"!|/ ////////| +----------------------+-----------------------------------+-----------+