RE: log buffer size and log file syncs
- From: "CRISLER, JON A" <JC1706@xxxxxxx>
- To: saurabh manroy <saurabhmanroy@xxxxxxxxx>
- Date: Mon, 30 Apr 2012 20:59:25 +0000
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@xxxxxxxxx]
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@xxxxxxx<mailto:JC1706@xxxxxxx>> 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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