Re: Update Statistics
Avichal A Narayan said:
> 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.
Don't run UPDATE STATISTICS MEDIUM on its own. Have you tried running only
UPDATE STATISTICS LOW DROP DISTRIBUTIONS and NOT running medium or high?
> ----- 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
>
--
Bye now,
Obnoxio
"C'est pas parce qu'on n'a rien ' dire qu'il faut fermer sa gueule"
- Coluche
A smile is a gift that is free to the giver and precious to the recipient.
But giving someone the finger is free too, and I find it more personal and
sincere.
sending to informix-list