Re: Global Cache and Enqueue Services statistics
- From: K Gopalakrishnan <kaygopal@xxxxxxxxx>
- To: Amir.Hameed@xxxxxxxxx
- Date: Tue, 31 Jul 2012 23:53:28 -0500
Amir,
The problem appears to be with Buffer busy waits at GC layer. 40 ms
range for gc buffer acquire is way too high and do you care to send
the awr to me.
Without going to additional details, do you think you can test the
same workload with _buffer_busy_wait_timeout=2. Just use ALTER SYSTEM.
-Gopal
On Mon, Jul 30, 2012 at 3:47 PM, Hameed, Amir <Amir.Hameed@xxxxxxxxx> wrote:
> Hi Gaja,
> Below are the top-5 wait events which are the same on all nodes:
>
> Top 5 Timed Foreground Events
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Avg
> wait % DB
> Event Waits Time(s) (ms) time Wait
> Class
> ------------------------------ ------------ ----------- ------ ------
> ----------
> db file sequential read 54,365,842 34,374 1 32.3 User I/O
> gc buffer busy acquire 461,651 18,904 41 17.8 Cluster
> enq: TX - row lock contention 11,506 15,269 1327 14.4
> Applicatio
> DB CPU 11,476 10.8
> gc current block busy 255,945 10,747 42 10.1 Cluster
>
> I am also investigating to see if the test was run the way it should have
> been because of the ' enq: TX - row lock contention' event. I have also
> identified statements that were suffering from the 'gc' waits shown above.
> The underlying segments of those statements have 'freelist groups' defined as
> '1'. This is an EBS system which has been around for a long time. It was
> upgraded from 11.0.3 to 11i several years ago and that is most likely why
> 'freelist groups' of most of the standard segments is '1'.
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