Re: Slow Query

On Thu, 29 Nov 2001 11:12:06 -0600, Vikram Dayanidhi <vikran_at_bay.uh.edu> wrote:

>I have a problem with a query thats been driving me crazy for the past few
>weeks. I hope someone can help me.
>
>We have 3 production databases - A, B, C. Database A supports a web-site,
>while the other 2 databases are for internal uses. Data from Database A is
>replicated to the other 2 databases.
>
>My problem is I have a batch job running on one of the internal databases,
>(database B) which is taking a long time to run. In particular, there is
>one query that runs against the replicated tables that takes about 2
>minutes to run on database B, but takes about only 20 seconds to run on
>database C. The replicated tables on both the databases have the exact
>same indexes.
>
>I noticed that the my query requires about 15000 disk reads on database B,
>where it uses about 5000 disk reads on database C. I checked the execution
>plans, and they are identical.
>
>I can't seem to figure out what's going on. I would appreciate it if
>someone would shed some light on this problem
>
>Thanks in Advance
>Vikram
>

Are the analysed statistics up to date on B? What about shared pool size? Are the tablespace extents the same? What about the file system and disk fragmentation? Lots of variables which could affect performance. Received on Sat Dec 01 2001 - 11:55:05 CST