Re: What's your opinion: ALL_ROWS vs FIRST_ROWS

"Armstead, Michael A" wrote:
>
> We're moving from RBO to CBO.
>
> For those of you who use CBO, what mode do you use FIRST_ROWS or ALL_ROWS?
> And why?
>
> My thinking is if it's a database where most of the querying is done on
> small sets of records, then we may want to use FIRST_ROWS. On the other
> hand, if our database is used to generate sizable reports, we might use
> ALL_ROWS.
>
> I also understand that we can always change it per session (with alter
> session) and per query (with hints).
>
> Michael Armstead
> Principal Database Administrator, OCP-Certified
> World Wide Corporate IT Database Administration
> GlaxoSmithKline
>

Michael,

   FIRST_ROWS is when you have a nervous user waiting for his/her results - OLTP. ALL_ROWS is when you want all the job to be done as fast as possible - Batch. This is the broad picture. Now, if your queries are used to generate HTML pages, this is no longer OLTP - it's batch since you cannot return the page before the query is completed.

HTH, Stephane Faroult
Oriole Software

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Author: Stephane Faroult
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