Hi Steve,
According to Pablo's question:
"If I recall correctly a log file sync wait is the time
it takes to write log buffer blocks to disk when a
user issues a commit. And this event "only" increments
when a user issues a commit, am I correct ?"
What I think is that a 'log file sync' is not only producced by a
'user commit'.
I think that the difference between these 2 values might be because
'user commits' does no take in consideration 'piggyback' writes due to
multiple commits (so it counts 7 commits and only one log file sync, for
instance) and syncs needed by the DBWR (who will also wait in log file
sync) and are not counted in 'user commits' statistic.
Am I forgetting some other cause? or I'm missing something else?
TIA
Diego
----- Original Message -----
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
Sent: Wednesday, October 17, 2001 10:35 PM
> Hi Pablo and list,
>
> The idea is that commits are routine, and you should expect approximately
1 'log file sync' wait per commit, and the
> duration of that wait should be approximately the same as the average 'log
file parallel write' time. My thinking was
> that if there are more 'log file syncs' or if they take longer, then that
indicates a "non-routine" performance problem.
> However, this is no longer as reliable as it used to be under Oracle7.
Under 8i (and possibly 8.0) if LGWR is using
> asynchronous I/O, then the 'log file parallel write' time may not include
all of the I/O time.
>
> @ Regards,
> @ Steve Adams
> @ http://www.ixora.com.au/
> @ http://www.christianity.net.au/
>
>
> -----Original Message-----
> Sent: Thursday, 18 October 2001 2:16
> To: Multiple recipients of list ORACLE-L
>
>
> Hi list,
> I don't quite understand this Steve Adams script
> (in fact, it's just a part of the script
> resource_waits.sql):
>
> select
> 'non-routine log file syncs',
> e.total_waits,s.value,
> round(e.average_wait * greatest(e.total_waits -
> s.value, 0)) val,
> e.average_wait
> from
> sys.v_$system_event e,
> sys.v_$sysstat s
> where
> e.event = 'log file sync' and
> s.name = 'user commits'
> order by 2 desc;
>
> Why does it substract user commits to total log file
> sync waits?
>
> If I recall correctly a log file sync wait is the time
> it takes to write log buffer blocks to disk when a
> user issues a commit. And this event "only" increments
> when a user issues a commit, am I correct ?
>
> Can anybody explain this problem?
>
> thanks, Pablo
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Steve Adams
> INET: [EMAIL PROTECTED]
>
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--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Diego Cutrone
INET: [EMAIL PROTECTED]
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San Diego, California -- Public Internet access / Mailing Lists
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