log file sync

From: "Hameed, Amir" <Amir.Hameed@xxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Date: Mon, 6 Aug 2012 15:55:46 -0400

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

 


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Follow-Ups:

Re: log file sync
From: David Fitzjarrell

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