Comments on: Tuning ‘log file sync’ Event Waits

By: akas

akas — Wed, 24 Feb 2010 11:19:45 +0000

3600 seconds is one hour. Hope you get it now.

By: bipin

bipin — Fri, 12 Feb 2010 16:20:04 +0000

Hi,
I didnot get this.
On average, 27021/3600 = 7.5 processes

from where we are getting the value of 3600 ?
my awr snapshot time is for 1800seconds.
can u please let me know why we divided the value with 3600

thanks.
bipsy

By: oracle dba

oracle dba — Fri, 12 Feb 2010 15:00:11 +0000

Your blog help me a lot – Thanks

By: David

David — Wed, 03 Feb 2010 03:26:44 +0000

Excellent post.Thanks.

By: Anji

Anji — Wed, 25 Nov 2009 16:16:18 +0000

Very nice and very clear explanation…..Thanks a lot……

By: Saikrishna

Saikrishna — Tue, 18 Aug 2009 03:28:24 +0000

very nice explanation. Thanks a lot!

By: Uday

Uday — Tue, 30 Jun 2009 15:47:16 +0000

Very simple and nice explanation. Thanks a lot!

By: shamsudeen

shamsudeen — Mon, 30 Jun 2008 23:08:37 +0000

Hi Alex
Good catch. Yes, you are correct about that line. semnum should be 118 in that line. Thanks.

Thanks
Riyaj

By: Polarski Bernard

Polarski Bernard — Mon, 30 Jun 2008 06:47:12 +0000

Beside playing with commit_write, there is very little action that a production DBA can do about logfile synch. Usually, once you diagnose too much commit, the lead developer replies that that the application is built like that and amen.

By: Alex Gorbachev

Alex Gorbachev — Sun, 29 Jun 2008 13:28:35 +0000

Riyaj, Excellent post indeed! My favorite part is LGWR & semaphores overview. Hey, I think I noticed a wrong trace line in step 4 of Signals, Semaphores and LGWR section...

After successful completion of the write(s), LGWR posts a semaphore of the waiting process using the semctl command.
22459/1: semctl(9, 15, SETVAL, 1)                   = 0

If I understand correctly, the semaphore with sem_num 118 -- the one that server process is waiting on inside log file sync.