Thank you for inputs. Unfortunately I cannot go ahead with the test
scenario in the page as this database is an AWS RDS (which I already hate
for obvious reasons) and I cannot access the x$ views.
Can someone help me provide an insight on how much the performance is being
impacted as the average wait caused by cursor pin : S is 14 ms while we are
in parallel trying to reduce the number of calls (App side).
Any help is very appreciated.
On Sun, Jun 18, 2017 at 9:45 AM, Mladen Gogala <gogala.mladen@xxxxxxxxx>
On 06/18/2017 11:52 AM, GG wrote:
W dniu 2017-06-18 o 17:41, Ravi Teja Bellamkonda pisze:
We have a 126.96.36.199 database and recently we are facing a performance
issue. Wait event is cursor pin:s. A particular sql query is executed
Executions - 31,173,028
Total Elapsed Time - 2033.64 s
Can some provide some input a way to diagnose the root issue. I see that
the no of executions are very high.
Thanks & Regards,
Ravi Teja Bellamkonda
start here :
Nice page, however not very useful to find a medication. Pin:S is waiting
for a pin in the shared mode on the cursor. I have played with another pin,
"buffer busy wait", deliberately starting 10 threads from a Perl script,
all modifying the same blocks in the table and performing rollback at the
end. The table was SCOTT.EMP, so that the entire PK index fitted into a
single block. I got my buffer busy waits all right, but the question is
what to do about them? The solution I have found is to use multi-threaded
version of Oracle 12c on Linux. Pins are much cheaper on the multi-threaded
version then on the multi-process version. I have not yet had time to
verify the reason I suspect, I am flying to the customer this afternoon and
will probably not be able to verify it until mid-July, but I suspect that
the multi-process pin mechanism is using semaphores, while multi-threaded
does not. It will take a session with strace to verify that. I have already
written about multi-threaded execution here:
However, I have not yet verified the details of the pin mechanism. It is
my ASSUMPTION that multi-threaded version doesn't use semaphores, as
opposed to the multi-process mechanism. That remains for me to do.
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