RE: KCL gc element parent latch
- From: Rajesh Rao <Rajesh.Rao@xxxxxxxxxxxx>
- To: Tanel Poder <tanel@xxxxxxxxxx>
- Date: Wed, 16 Dec 2009 12:34:13 -0500
Thank you Tanel.
"so if you have lots of GC ops, these latches will be used. Fix the GC traffic
and the latching problem will go away."
So, those waits would be an effect, rather than the cause leading to gc cr
request waits. These waits themselves are not significant. We see fast object
checkpoints as well as this KCL latch that seems to precede most of the gc cr
request waits we see. We know the fix for the gc waits.
Thank you for the script. That goes into the same directory where I have the
snapper one stored :)
Raj
From: Tanel Poder [mailto:tanel@xxxxxxxxxx]
Sent: Wednesday, December 16, 2009 12:16 PM
To: Rajesh Rao
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: KCL gc element parent latch
GC operations may require changes to PCM locks / lock elements. The lock
element array (V$GC_ELEMENT) is protected by gc element latches... so if you
have lots of GC ops, these latches will be used. Fix the GC traffic and the
latching problem will go away.
How significant % of your sessions response time is spent waiting for this
latch?
If you see significant waits for that latch, you can run latchprofX to gain
undersanding who are the main holders of these latches and which kernel
functions cause the latches to be held the most etc:
http://blog.tanelpoder.com/2008/07/23/advanced-oracle-troubleshooting-guide-part-8-even-more-detailed-latch-troubleshooting-using-latchprofx/
Tanel
On Wed, Dec 16, 2009 at 4:27 AM, Rajesh Rao
<Rajesh.Rao@xxxxxxxxxxxx<mailto:Rajesh.Rao@xxxxxxxxxxxx>> wrote:
10.2.0.3 RAC. Looking to get more insight into this latch as I see seek to
troubleshoot and check for co-relation to an issue with sessions experiencing
"gc cr request" waits. Especially, what causes sessions to wait on this latch?
Regards
Raj
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