Notes in-line
--
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The educated person is not the person
who can answer the questions, but the
person who can question the answers -- T. Schick Jr
Next public appearance2:
March 2004 Hotsos Symposium - Keynote
March 2004 Charlotte NC - OUG Tutorial
April 2004 Iceland
One-day tutorials:
http://www.jlcomp.demon.co.uk/tutorial.html
Three-day seminar:
see http://www.jlcomp.demon.co.uk/seminar.html
____UK___February
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
"Ron Boggs" <rboggs_at_endian-networks.com> wrote in message
news:e53f59be.0401131500.40e83290_at_posting.google.com...
> Statspack will tell me there were 'X' number of log file sync timeouts
> between snapshots....
>
> 1) Is there any way to find out exactly when each timeout occurred?
> I'm trying to determine if there is correlation between these timeouts
> and spikes in app performance.
>
Exactly - no, to within N seconds - yes.
If you know what you want to look for (e.g. v$system_event
for event "log file sync") then you could write a little pl/sql
procedure that loop for 30 minutes, doing a select for
that item every 10 seconds, and printing the delta from
the last cycle using utl_file. If it's really important to
get the answer, this is the cheapest option.
> 2) After a timeout (1000ms in this case) what happens? It's
> obviously still waiting on the post back from the log writer process.
> Does it just switch context to another session and check again when
> active?
You may be misinterpreting statspack - how are you
inferring that you had a timeout that lasted 1000ms ?
I'll guess for the moment that you've had many waits,
including one timeout, totallling 1,000 ms. (If this
is with a couple of dozen busy processing running
over a period of 15 minutes, I wouldn't be too bothered).
To enter a wait, a process sets an alarm clock (typically
in the small number of centiseconds, though some are 1,
2, or 3 seconds, and a few are five minutes) then goes to
sleep waiting for a callback. If the callback comes before
the alarm goes off, the wait time is recorded; if the alarm
goes off first, a timeout (and the wait time) is recorded.
Usually on a timeout, the process resets the alarm clock
and goes back to sleep.
>
> Thanks,
> Ron Boggs
> St. Louis
Received on Fri Jan 16 2004 - 08:34:29 CST
