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Replies: 4 - Pages: 1 - Last Post: Aug 28, 2006 11:36 AM Last Post By: Kevin Krause

hzhang@siebel.com

Posts: 1
Registered: 06/17/02

How to clear buffer cache for performance tuning
Posted: Jun 17, 2002 12:07 PM

I am doing performance tuning, after the first run, the data is loaded into buffer cache, so the second run will take shorter time, my question is, how to clear the buffer cache so the second run can be compared at the same basis with the first run? Maybe this is too simple for you, but I am new in this area, please help.

vasuhg

Posts: 2
Registered: 02/14/00

re:How to clear buffer cache for performance tuning
Posted: Jun 18, 2002 1:28 PM

in response to: hzhang@siebel.com

Find out the tables (and the tables behind the views) that the data in the buffer cache is loaded from. Using this info, get the tablespaces these tables belong to. Bring these offline - 'ALTER TABLESPACE <tablespace_name> OFFLINE;' for all the tablespaces. And bring them online - 'ALTER TABLESPACE <tablespace_name> ONLINE;' for all the tablespaces. This will invlidate all the blocks belonging to the above tablespaces.

sikandar_h

Posts: 30
Registered: 06/08/00

re:How to clear buffer cache for performance tuning
Posted: Aug 25, 2002 3:04 AM

in response to: vasuhg

Shutdown and start the db as it will clear all the SGA.

user527295

Posts: 1
Registered: 08/27/06

Re: How to clear buffer cache for performance tuning
Posted: Aug 27, 2006 6:43 PM

in response to: hzhang@siebel.com

Try this running this...you should only do this against a test db.

ALTER SYSTEM FLUSH BUFFER_CACHE;

Cheers, Jon

Kevin Krause

Posts: 505
Registered: 08/15/00

Re: How to clear buffer cache for performance tuning
Posted: Aug 28, 2006 11:36 AM

in response to: hzhang@siebel.com

take your results with a grain of salt. Remember in the "real world", your system may have some of these blocks cached, stats may be different, the planets may not be aligned.

Try to validate your performance tweaks in an environment that is as close as possible to your production system.

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