Re: any possible replacement view for v$system_event/x$kslei
- From: "kyle Hailey" <kylelf@xxxxxxxxx>
- To: zhuchao@xxxxxxxxx
- Date: Tue, 5 Feb 2008 13:55:58 -0800
querying v$system_event, even at 10 second intervals should be cheap.
You say it "is very CPU consuming". Have you quantified the amount of
CPU it uses?
S-ASH, or simulated ASH, used about 1% of 1 CPU when I had 10 session
active an that was polling every second. In S-ASH default install I
poll every 3 seconds and if you are using version 10g, I just query
v$session instead of joining to v$session_wait so it is even cheaper.
If you need something cheaper, for some reason, then reading the SGA
is the way to go, but in your example, I can't imagine any reason to
sample v$system_event that fast. On the other hand, sampling v$session
on 10g to reproduce ASH is very apealing - it avoids the license issue
of ASH and it provides all the rich performance data, multi
dimensional aggregations and drilldowns we get from ASH.
(v$system_event is pre-aggregated data that provides no possibilites
of drilling into the sesions/users involved, there sql nor the
detailed p1,p2,p3 needed to solve the majority of wait event problems.
Best Wishes
Kyle Hailey
http://perfvision.com
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