RE: log file sync

From: Timur Akhmadeev <Akhmadeev_at_NetCracker.com>
Date: Tue, 7 Aug 2012 09:56:38 +0000
Message-ID: <FFB456FD9AC03C48B943326F553A70AC504A7E7E_at_umaildb2.netcracker.com>

Hi
Refer to this post: http://kevinclosson.wordpress.com/2007/07/21/manly-men-only-use-solid-state-disk-for-redo-logging-lgwr-io-is-simple-but-not-lgwr-processing/

Regards
Timur Akhmadeev

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Hameed, Amir Sent: Monday, August 06, 2012 23:56
To: oracle-l_at_freelists.org
Subject: log file sync

Hi all,
My AWR report shows 'log file sync' among the top five events. When I look at the 'Foreground Wait Events', I see the following:

                                                             Avg

                                        %Time Total Wait    wait

Waits % DB

Event                             Waits -outs   Time (s)    (ms)

/txn time

• ------------ ----- ---------- ------- -------- ------

log file sync                   166,765     0      3,575      21

1.1 3.3

The 'Background Wait Events' section shows the following for 'log file sync' and 'log file parallel write':

                                                             Avg

                                        %Time Total Wait    wait

Waits % DB

Event                             Waits -outs   Time (s)    (ms)

/txn time

• ------------ ----- ---------- ------- -------- ------

log file sync                        56     0          1      11
0.0     .0

log file parallel write         221,159     0          1       0
1.4     .0

My question is that if the LGWR is not waiting for the 'log file parallel write' during synchronous writes (avg. wait time=0) then why is the average wait time of 'log file sync' event for the foreground and background processes (DBWR, LMS etc.) is high?

Thanks

Amir

--
http://www.freelists.org/webpage/oracle-l




________________________________
The information transmitted herein is intended only for the person or entity to which it is addressed and may contain confidential, proprietary and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.
--
http://www.freelists.org/webpage/oracle-l

Received on Tue Aug 07 2012 - 04:56:38 CDT