Impact of an incorrect CPUSPEEDNW
- From: "Teehan, Mark" <mark.teehan@xxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 15 Jan 2010 12:21:57 +0800
I am reviewing system statistics for a number of database servers
running various 10g releases. Most are using default NoWorkload
settings; but I've noticed something odd: some databases have
unexpectedly low values for CpuSpeedNw even though they are running on
identical servers. This is because they were migrated from older servers
and sys stats were not regathered for the new servers.
The database will not automatically recollect system stats unless they
are explicitly deleted. This seems an oversight: given that some values
like CPU_COUNT are rechecked every time the database starts; I wonder if
CpuSpeedNw should also be rechecked automatically.
In some cases the numbers are about 30% what they should be; which means
that the optimizer calculations are incorrect. I wonder if regathering
them - I don't want to do this unless I can confirm that it will make a
significant difference - after all the database has been subsequently
tuned to run with a lower CpUSpeedNw setting.
Something else that I'm checking- if you do an RMAN clone, or an import
FULL=Y, does it pull over the system stats too? I also posted this to
forums.oracle.com.
Any ideas?
Mark
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