alex, if you use choose and analyze you table every night. cbo will be
used. hint overwrite the access chosed path by cbo. cbo choose tablescan
and hint overwrite with index access.
ted chyn
In article <_MEH3.22331$1E2.172245_at_ozemail.com.au>,
"Alex Daman" <alex_damanakis_at_exe.com.au> wrote:
> Hello All,
>
> I am fairly new in the ORACLE world and need some input with a problem
we
> are facing.
>
> Oracle Version : 7.3.4
> Platform : IBM AIX UNIX 4.3
>
> The Oracle optimizer does not choose the index path that is reported
in the
> query plan unless the SQL statement contains hints. I know this is
happening
> because the statement without the hints takes 2minutes to run as
compared to
> 3 seconds with the hints.
> You might say then, "Use Hints!" but I really need to understand what
is
> going on here because I dont want to go and modify every program thats
> querying the database.
> I also do not believe that a RDBMS product like Oracle has an
optimizer that
> behaves this way.
>
> OPTIMIZER_MODE is set to CHOOSE and we run ANALYZE every night.
>
> I have also read somewhere that this can be caused by type casting. I
have
> checked the application and this is not the case.
>
> Can anyone please give me any other reasons for the optimizer to
behave this
> way.
>
> Thanks in advance.
>
> Alex
>
>
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Received on Tue Sep 28 1999 - 08:50:43 CDT
