Re: OPTIMIZER CHOOSE vs. FIRST_ROWS

You say the databases have the same amount of data, but is the data distributed in the same way. Was one of the databases populated via an import / export of the other database ? FIRST_ROWS tends to favour index access, could the indexes on one of the databases be in need of a rebuild (i.e the height of the index is >=4 or has there been many updates / deletes affecting the index leaf blocks ?) The import to the second database will have rebuilt these indexes.

Have you done an explain plan tkprof on the query to prove that thy are using the same access path ??

HTH NeilC
jacksnews_at_my-deja.com wrote in message <7u1ts7$iud$1_at_nnrp1.deja.com>...
>Hello,
>
>I 've two databases with the same application, on two identical servers.
>The databases are containing the same amount of data.
>They are using the same indexes and datamodels.
>They are analysed every night.
>
>BUT:
>
>When I'm using the FIRST_ROWS optimizer the server a is
>up to 100 times slower than the server b which is using the optimizer
>first_rows, too. With the optimizer choose on server a
>it works with the same performance like server b.
>
>So, I have to use choose for server a and first_rows for the other
>one.
>
>Can anyone tell me why ?
>
>Thanks
>Jacques
>
>
>Sent via Deja.com http://www.deja.com/
>Before you buy.
Received on Wed Oct 13 1999 - 08:06:18 CDT