RE: log buffer size and log file syncs

From: CRISLER, JON A <JC1706_at_att.com>
Date: Mon, 30 Apr 2012 20:59:25 +0000
Message-ID: <9F15274DDC89C24387BE933E68BE3FD3252D9F_at_MISOUT7MSGUSR9D.ITServices.sbc.com>

I don't think "wait for scn ack" is a factor in this issue. I previously looked at the bugs you cited and our version is supposedly patched beyond that level (i.e. fixed in 11.1.0.7.3 and we are higher than that).

                                                             Avg
                                       %Time Total Wait    wait    Waits   % bg
Event                             Waits -outs   Time (s)    (ms)     /txn   time


-------------------------- ------------ ----- ---------- ------- -------- ------

latch: ges resource hash l        1,758     0          0       0      0.0     .0
db file parallel read                 7     0          0      12      0.0     .0
latch: row cache objects          3,588     0          0       0      0.0     .0
gc cr block congested                 3     0          0      25      0.0     .0
enq: TA - contention                104     0          0       1      0.0     .0
gc current split                      7     0          0       9      0.0     .0
enq: JS - queue lock                  3     0          0      19      0.0     .0
PX Deq: Signal ACK RSG              264    48          0       0      0.0     .0
wait for scn ack                      7     0          0       6      0.0     .0

                                                             Avg
                                        %Time Total Wait    wait    Waits   % DB
Event                             Waits -outs   Time (s)    (ms)     /txn   time


-------------------------- ------------ ----- ---------- ------- -------- ------

log file sync                   162,278     0      5,703      35      0.9   17.0

From: saurabh manroy [mailto:saurabhmanroy_at_gmail.com] Sent: Monday, April 30, 2012 4:17 PM
To: CRISLER, JON A
Cc: oracle-l
Subject: Re: log buffer size and log file syncs

Because its 11gR1 and RAC, I wonder how much time is *wait for scn ack* contributing to the log file sync wait? There are few bugs on top of 11gR1 related to broadcast on commit scheme of SCN propagation, that you might want to check:

Bug 8490879 - Long "log file sync" latencies due to broadcast on commit scheme
Bug 7716356 - Long "log file sync" latencies with broadcast on commit scheme in RAC
Bug 7610362 - Long "log file sync" waits in RAC with broadcast on commit in RAC

Regards,
Saurabh Manroy

In case you are interested, I have written about log file sync waits in rac here: http://tinyurl.com/89k6jem<http://tinyurl.com/89k6jem>

On Mon, Apr 30, 2012 at 4:56 PM, CRISLER, JON A <JC1706_at_att.com<mailto:JC1706_at_att.com>> wrote: Interesting thoughts Tanel: in this case of this specific app, the majority of the work is made of up small commits to a handful of tables on a 6 node RAC cluster. I/O times are generally quite good, and with 32 cores per node the CPU and load average is very low. Its 11gR1 - I was wondering if some of the tweaks to put LGWR at "real time" priority that are mentioned for 10g also apply to 11g.

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Received on Mon Apr 30 2012 - 15:59:25 CDT