Re: db file sequential/scattered read - physical or logical io or both?

From: Andrew Kerber <andrew.kerber_at_gmail.com>
Date: Sun, 13 Jun 2010 18:28:23 -0500
Message-ID: <AANLkTin36v991rZCGPSuwR0OxLJY7Wsp6xOdJzIOn08M_at_mail.gmail.com>

On the dba_hist_sysstat table, the stat name you want for a physical read is 'physical read'

On Sun, Jun 13, 2010 at 5:45 PM, Oracle Dba Wannabe < oracledbawannabe_at_yahoo.com> wrote:

> 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
> >
> >
> >
> >
> >--
> >http://www.freelists.org/webpage/oracle-l
> >
> >
>
>
>
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

-- 
Andrew W. Kerber

'If at first you dont succeed, dont take up skydiving.'

--
http://www.freelists.org/webpage/oracle-l

Received on Sun Jun 13 2010 - 18:28:23 CDT