Re: CBO optimizer

>>
>> Are there other solutions to this problem???, can you give me suggestions
>> ???
>
> I have a question, a suggestion and a comment.
>
> The question is, do your tables really change in number of rows
> drastically downwards as well as upwards? As a sweeping generalisation
> large tables tend to stay large and increase in size and small tables tend
> to stay small. The behaviour you describe would in my experience be a
> little unusual.

yes my tables change upwards,and then downwards... and then upwards..then downwards...

>
> The suggestion is, you know that you can set stats using dbms_stats? If
> so, then your second suggestion seems likely to make sense. calculate the
> stats when data is 'worst' for performance and then stick with that. Get
> your worst performing time to perform adequately, and the chances are
> (though oddities do arise) that lighter load times will be not as good as
> they could be , but still OK as well.
>
> The comment. I don't see anywhere that Oracle suggest 'calculating
> statistics often'.

Yes, you are right, but oracle suggest to calculate statistcs (i use dbms_stats) when the data has been changed and the previous one... so if the data changes frequently..... (this is a my deduction...)

>
>
> --
> Niall Litchfield
> Oracle DBA
> http://www.niall.litchfield.dial.pipex.com
>
Received on Fri Dec 03 2004 - 12:16:24 CST