Re: db file sequential/scattered read - physical or logical io or both?
- From: Oracle Dba Wannabe <oracledbawannabe@xxxxxxxxx>
- To: oracledbawannabe@xxxxxxxxx, oracle-l@xxxxxxxxxxxxx
- Date: Sun, 13 Jun 2010 15:45:20 -0700 (PDT)
I suppose what I'm trying to say here is that if the same wait event is issued
regardless of a physical or logical io request, how can I determine if the io
subsystem is returning blocks at s reasonable service time. Assuming an idle
system other than the report, would times under 5ms be cache hits and times
over be physical. Further anything over 10ms would be a bad service time ?
appreciate any input on this
Thanks
On Mon, 14 Jun 2010 06:31 SGT Oracle Dba Wannabe wrote:
>Hi,
>So I have an idle system, where I run a sql report. The report takes an hour
>to run. I look at the awr report (30 min interval), and see the io wait events
>for sequential and scattered reads. The first has an avg wait time of 7ms the
>second 10ms. These waits as I understand it are physical io requests -
>correct? The p1 and p2 parameters point to file and block numbers so I guess
>that makes sense. Anyway I rerun the same report, look at the new awr and now
>see the same wait events, only with much smaller wait times. Which means data
>was read from cache - if that's the case why are the same wait events issued?
>it seems a bit confusing that way.
>Thanks
>
>
>
>
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