Jack You are right keeping in mind your application and variation of data in different tables. I just mentioned 30% as most agreed percentage for estimate. I think Dennis gave you a more pracitcial answer yesterday.
Regards Rafiq Reply-To: [EMAIL PROTECTED] To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> Date: Tue, 21 May 2002 15:19:31 -0800 Hi Rafiq, We have been using 35 percent on our warehouse, even on our fact partitions. Now that I have thought about it for a while, that seems like a lot given the volume of data. If a representative sample can be gathered with 10,000 or 50,000 or 100,000 rows, and our fact partitions have millions of rows each, seems like we could go 1% on our analyze and it would be within acceptable tolerances. /jack --- Mohammad Rafiq <[EMAIL PROTECTED]> wrote: > The most of the list memeber agrees on estimate with > 30%.... > > Regards > Rafiq > > > > > Reply-To: [EMAIL PROTECTED] > To: Multiple recipients of list ORACLE-L > <[EMAIL PROTECTED]> > Date: Tue, 21 May 2002 13:43:33 -0800 > > Hi all, > > Did some investigation about statistical sampling > this > weekend since we are going to optimize our analyze > process soon, and would like some input from all you > orabrains on this one. > > I opened a TAR with Oracle asking about the sampling > algorithm of stats collection, and they assured me > it > was random. > > The goal of analyze...estimate is to collect stats > that are representative of the data population as a > whole using a given sample set. Since analyzing > tables > takes up resources (does sorts to order the data for > investigation) the fewer rows you use in estimate, > the > less system resources you use and the faster the > analyze will go. > > Since our goal is to get as small a sample as > possible > and still have stats that are representative, my > contention is that we could start by finding what > the > margin of error will be for each sample size and > gauge > our tolerance for it. > > One standard way to calculate margin of error for a > given sample is by using this formula: > > M = 1/SQRT(N) > > where: > M = margin of error > N=sample size > > So, if we can tolerate stats that have a 1% a margin > of error (will deviate from representative of the > whole population by 1%), our sample size should be > 10,000 rows. > > Also, a corollary (not a toyota corollary, though) > to > this would be that the more rows you add to your > sample, the closer to representative your sample > will > be. So, in order to test whether your sample is > representative enough, you could analyze using > either > estimate 49% or compute, take a snapshot of the > stats, > and then compare the stats from a 10,000 row > estimate > to those. Then, add rows to your estimate until you > are satisfied with the stats. > > This of course is a pie in the sky mathematical > model, > but seems like a reasonable place to start with > testing. > > Input? Input? Buhler? Buhler? > > > /jack silvey > > > __________________________________________________ > Do You Yahoo!? > LAUNCH - Your Yahoo! Music Experience > http://launch.yahoo.com > -- > Please see the official ORACLE-L FAQ: > http://www.orafaq.com > -- > Author: Jack Silvey > INET: [EMAIL PROTECTED] > > Fat City Network Services -- (858) 538-5051 FAX: > (858) 538-5051 > San Diego, California -- Public Internet > access / Mailing Lists > -------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an > E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of > 'ListGuru') and in > the message BODY, include a line containing: UNSUB > ORACLE-L > (or the name of mailing list you want to be removed > from). 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You may > also send the HELP command for other information > (like subscribing). __________________________________________________ Do You Yahoo!? LAUNCH - Your Yahoo! Music Experience http://launch.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Jack Silvey INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). 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