RE: flush shared_pool and query performance

From: Asif Momen <asif_oracle_at_yahoo.com>
Date: Thu, 3 Apr 2008 16:45:43 -0700 (PDT)
Message-ID: <263404.75914.qm@web56603.mail.re3.yahoo.com>

Hi,

Is CURSOR_SHARING set to FORCE?

It could be the reasons.

Regards

Asif Momen
http://momendba.blogspot.com

genegurevich_at_discover.com wrote: OK. I am still confused here.

Here is what I do (oracle 10.2.0.2);

execute a SQL - select col1, col2 from table where col3='1123' - completes in about 0.01s
execute a SQL - select col1, col2 from table where col3='4567' - completes in about 0.01s
alter system flush shared_pool;
execute a SQL - select col1, col2 from table where col3='1123' - completes in about 0.3
execute a SQL - select col1, col2 from table where col3='1123' - completes in about 0.01s
execute a SQL - select col1, col2 from table where col3='4567' - completes in about 0.01s

Why would the third SQL complete that fast. I have a different SQL because of the value 4567 (and I don't
use bind variables), so shouldn't this be a hard parse too?

thank you

Gene Gurevich

                                                                           
             "Bobak, Mark"                                                 
             
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                                       RE: flush shared_pool and query     
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             Mark.Bobak_at_proque                                             
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Sure, I don't think that's unreasonable at all. As an added confirmation, if you have 0.01 secs, and then you flush and first execution is 0.3 secs, does the second execution after the flush go back to 0.01 secs? If so, then the difference is the hard parse.

-Mark

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Mark J. Bobak
Senior Database Administrator, System & Product Technologies ProQuest
789 E. Eisenhower, Parkway, P.O. Box 1346 Ann Arbor MI 48106-1346
+1.734.997.4059 or +1.800.521.0600 x 4059 mark.bobak_at_proquest.com
www.proquest.com
www.csa.com

ProQuest...Start here.

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of genegurevich_at_discover.com
Sent: Thursday, April 03, 2008 5:40 PM
To: oracle-l_at_freelists.org
Subject: flush shared_pool and query performance

Hi all:

I am noticing that the same SQL executed before and after 'alter system flush shared_pool' completes in VASTLY
different time - 0.01s before the command and 0.3s after the command. I wonder why is that. When I flush the
shared_pool, the library cache is flushed and so my SQL needs to be reparsed. Is that reasonable for parsing to take 0.3s?

thank you

Gene Gurevich

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http://www.freelists.org/webpage/oracle-l Received on Thu Apr 03 2008 - 18:45:43 CDT