RE: FILLFACTOR

Responses Below: -----Original Message----- From: Thanh [mailto:tqma@my-deja.com] Sent: Wednesday, September 27, 2000 9:12 AM To: informix-list@iiug.org Subject: FILLFACTOR Hi, The 'Informix Handbook' seems to indicate if more inserts are to be expected in the future, then the FILLFACTOR should be small to improve insertion performance. My questions: 1. How to determine that a fillfactor is (or not) optiomal ? Monitor your index pages, determine how often an index page is added to the b-tree structure. You can run oncheck to determine the number of index pages as well as the number of levels. 2. If I am going to change the FILLFACTOR in the onconfig for a running system, then can I just bounce IDS or I have to do something else ? The FILLFACTOR in onconfig is used as the default fillfactor whenever you create the index. You can also specify the FILLFACTOR whenever you create an index. 3. If the FILLFACTOR is 50, then I can understand that when a page is full, it will be split into 50/50. How does IDS split the page when the FILLFACTOR is, say, 60 or 80 ? FILLFACTOR is only applicable when you create an index. For example is you set FILLFACTOR to 50. During index creation Informix will only use 50% of each index page. When data is inserted, the key for the index is also added to the index page until the index page becomes full or reaches a point wherein Informix has to split the contents of the page in other index pages. Thanks, Thanh Sent via Deja.com http://www.deja.com/ Before you buy.

Don, Thanks for responding. A few more questions follow Thanh In article <8qtdk2$ci5$1@news.xmission.com>, Don Ignacio <dignacio@openratings.com> wrote: > > Responses Below: > > -----Original Message----- > From: Thanh [mailto:tqma@my-deja.com] > Sent: Wednesday, September 27, 2000 9:12 AM > To: informix-list@iiug.org > Subject: FILLFACTOR > > Hi, > > The 'Informix Handbook' seems to indicate if more inserts are to be > expected in the future, then the FILLFACTOR should be small to improve > insertion performance. My questions: > > 1. How to determine that a fillfactor is (or not) optiomal ? > > Monitor your index pages, determine how often an index page > is added to the b-tree structure. You can run oncheck to determine > the number of index pages as well as the number of levels. How do I determine how many keys an index page has ? > > 2. If I am going to change the FILLFACTOR in the onconfig for a running > system, then can I just bounce IDS or I have to do something else ? > > The FILLFACTOR in onconfig is used as the default fillfactor whenever > you create the index. You can also specify the FILLFACTOR whenever > you create an index. I guess the answer is 'to change the FILLFACTOR for existing indexes, they have to be dropped and re-created. Right ? > > 3. If the FILLFACTOR is 50, then I can understand that when a page > is full, it will be split into 50/50. How does IDS split the page > when the FILLFACTOR is, say, 60 or 80 ? > > FILLFACTOR is only applicable when you create an index. For example > is you set FILLFACTOR to 50. During index creation Informix will > only use 50% of each index page. When data is inserted, the key for > the index is also added to the index page until the index page > becomes full or reaches a point wherein Informix has to split > the contents of the page in other index pages. How Informix split the contents of the full page in other index pages was what I am after. Thanh Sent via Deja.com http://www.deja.com/ Before you buy.