Re: Update Statistics

While still on update statics.... so what is most advisable ??? ..To do update statistics medium first and then do update staticstics high ????? We encountered a problem when we did update statistics medium. After sometime the system gets very slow. Any advise ?? Avichal ----- Original Message ----- From: "Art S. Kagel" <kagel@bloomberg.net> To: <informix-list@iiug.org> Sent: Friday, June 10, 2005 8:25 AM Subject: Re: Update Statistics > Andrew Ford wrote: > <SNIP> > > > Am I wrong in thinking that to update statistics against a table you only > > need 3 update statistics statements. > > > > low - every column that appears in an index > > high - every column that heads an index and every column in a composite > > index that is the first column that differs when multiple indexes have the > > same columns at the head of the index (i.e. (a, b, c, d) and (a, b, c, e) > > run high for d and e) > > medium - every column not included in the high stats > <SNIP> > > Specific comments: > > medium - The medium should be done first and it can be done on all columns. > Because of the sampling algorithms used it's just as fast to do all > columns as to do the subset that's not heading indexes, so dostats just does > a MEDIUM on all columns first then overwrites the medium stats with high > stats where needed. > > low - Again, yes for stats quality, no for efficiency if you are running an > older release of IDS. > > high - Same comments as for low. On newer IDSs do it all together, on older > ones, break it up. > > Art S. Kagel > > sending to informix-list