RE: log file sync waits / slow response time at log switches
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <gcunningham@xxxxxxxxxxxxxxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 15 Feb 2008 14:07:57 -0500
After you figure out the best way to handle the dataguard sychronization
issues (several other comments in this thread seem productive, and I won't
make a comment on that unless I deeply understand your remote site business
continuation requirements and I've never seen that be a pro bono sized
task), you probably also want to add redo log groups. Even if you completely
remove the dataguard issues, you cannot start overwriting an online log that
has been used before it has been archived (sorry about stating the obvious).
But if you have plenty of online redo log groups to switch into to handle
peaked insert/update/delete load you can defer jambing up wrapping around
for a time equivalent to the extra space you invest. This of course dies
under its own weight if your steady state rate of updates
(insert/update/deletes) exceeds your steady state rate of archiving to your
slowest destination, or if your burst rate of updates exceeds your slowest
archiving rate for long enough. Fortunately Oracle doesn't die, it just
waits.
It appears you only have 3 groups. I suggest an even multiple of the number
of muliplexed independent stripe sets that make up your online redo log
volumes. If 12 is a big enough number to handle the peak load in excess of
archiving rate, that nicely handles 2, 3, and 4.
Regards,
mwf
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Gerald Cunningham
Sent: Thursday, February 14, 2008 2:22 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: log file sync waits / slow response time at log switches
Hi all,
My 10046 tracing is showing a lot of "log file sync" waits. Also, users log
files (processes are doing DML) are showing
spikes in response time that match the times of the log switches.
This is a physical Data Guard implementation with 1 primary / 1 standby.
Oracle 9.2.0.8 64-bit on Solaris.
From the alert log, it appears that Oracle is waiting until the redo
information has been written to the standby site
before it switches the primary's redo logs.
<snip>
Other related posts:
