Re: db file scattered read
- From: Mladen Gogala <gogala@xxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Sun, 15 Aug 2004 12:58:55 -0400
On 08/15/2004 12:48:21 PM, Wolfgang Breitling wrote:
> Mladen,
>
> Can you explain a bit what your example is intended to show in response to
> my post. As far as I can tell it merely confirms what I had been saying
> a) dynamic_sampling=4 does not necessarily guarantee that analyzed tables
> will be sampled.
> Both tables in your example have no statistics, so they DO get sampled
> once you force the CBO
Wolfgang, my impression was that your original statement was that dynamic
sampling
doesn't work. I just wanted to show that it does work, provided the use of CBO
is
forced. Unless the CBO is conscienceously forced, the database will use RBO if
none
of the tables have statistics. I'm experimenting with ALL_ROWS and and
OPTIMIZER_INDEX
parameters to get the desired database behavior. My ultimate goal is to convert
an 8i
database using RBO (forced directly by parameter and a periodic job that deletes
statistics from any new table) into a 10g database using CBO, without much
degradation
in query performance.
--
Mladen Gogala
Oracle DBA
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