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

From: Oracle Dba Wannabe <oracledbawannabe_at_yahoo.com>
Date: Sun, 13 Jun 2010 15:31:04 -0700 (PDT)
Message-ID: <906166.93049.qm_at_web113916.mail.gq1.yahoo.com>

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       
Received on Sun Jun 13 2010 - 17:31:04 CDT

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