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reduce the wait event for db file sequential read event [message #330616]

Mon, 30 June 2008 10:42

ankush_chawla
Messages: 136
Registered: November 2006

Senior Member

Hello

We see high waits events for the db file sequential read event in the statspack report . What i understand is that it is always a single block read which TYPICALLY happens during index scans .

So does tuning the indexes for the database like rebuiding them online would work. Can anybody explain in a better way what really it mean .

Thanks in advance

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Re: reduce the wait event for db file sequential read event [message #330618 is a reply to message #330616]

Mon, 30 June 2008 10:46

Mahesh Rajendran
Messages: 10707
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

>>So does tuning the indexes for the database like rebuiding them online would work
May be or may not be.
Actually, rebuilding the index does not constitute as tuning Smile

.
Are the table / Index stats updated?

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Re: reduce the wait event for db file sequential read event [message #330620 is a reply to message #330616]

Mon, 30 June 2008 10:47

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

http://www.orafaq.com/forum/t/88153/0/
Please read & follow posting guidelines as stated in URL above

>We see high waits events
At what specific value do the number of wait event become "high"?
Below what value are the number of wait events OK?

Is this value true for all/every Oracle installation & application?

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Re: reduce the wait event for db file sequential read event [message #330631 is a reply to message #330618]

Mon, 30 June 2008 11:46

ankush_chawla
Messages: 136
Registered: November 2006

Senior Member

Thanks for the reply.....

database is oracle 10g .kindly let me know does this event only related to indexes ? it is an OLTP system however stats are not collected since a month.
Would Collecting stats of the indexes would be sufficient ?
is any other step in addition to this to reduce the wait time for this event

Thanks and regards
ankush

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Re: reduce the wait event for db file sequential read event [message #330636 is a reply to message #330616]

Mon, 30 June 2008 12:18

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

Subject: WAITEVENT: "db file sequential read" Reference Note
Doc ID: Note:34559.1

https://metalink.oracle.com/metalink/plsql/f?p=130:14:10309953110723579762::::p14_database_id,p14_docid,p14_show_header,p14_show_help ,p14_black_frame,p14_font:NOT,34559.1,1,1,1,helvetica

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Re: reduce the wait event for db file sequential read event [message #330639 is a reply to message #330631]

Mon, 30 June 2008 12:41

Mahesh Rajendran
Messages: 10707
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

First update the stats on tables and indexes using dbms_stats.
Try your operations again.
If problem persists, look into the metalink doc suggested.

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Re: reduce the wait event for db file sequential read event [message #330640 is a reply to message #330616]

Mon, 30 June 2008 12:47

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

>If problem persists
???
NO evidence of any problem has been posted; just a claim the value is/was "high".

While a performance problem may exist, I seriously doubt it involves "db file sequential read" waits.

Ready, Fire, Aim!

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