Re: high log file sync wait
- From: Suya <suya.huang@xxxxxxxxx>
- To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 4 Dec 2012 17:18:13 +0800
I compared the system statistics we got before with the current one:
the first one is the metric before, the second is the metric we have now,
and the third value is the percentage increased.
redo blocks written
66,777,507
45,417,168
-32%
in our previous test, the application TPM is higher, thus the redo blocks
written is higher, this is reasonable. however, the following metrics seems
abnormal:
redo blocks checksummed by FG (exclusive)
4,122,706
8,741,271
112%
redo synch long waits
9,759
106,017
986%
redo synch time
26,950,595
35,266,236
31%
redo synch time (usec)
269,505,943,171
352,662,539,336
31%
redo write broadcast ack count
39,923
96,618
142%
redo write broadcast ack time
254,688,838
686,018,713
169%
redo write broadcast lgwr post count
1
1,142
114100%
anyone has any clue about what does the above metrics mean and where is the
bottleneck of a LGWR SYNC wait?
2012/11/26 Suya <suya.huang@xxxxxxxxx>
> Hi,
>
> I have a four-node RAC system, the workload runs against the database
> waits on log file sync heavily, average wait time is 82.41 ms, account for
> 75% DB time. The system CPU resource is rich enough, average 70% idle time.
>
> similar testing was done previously, which has log file sync wait with
> average 40 ms, and because the CPU resource shortage, this time, we added
> two logical CPU to the system. but see that the log file sync wait event
> was even worse.
>
> any ideas on what else I should check in the AWR report?
>
> Thanks!
> Suya
>
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