FAQ
Hi, Charlotte.

One "db file scattered read" wait would mean physical reads of several
blocks, aka multi block I/O.

Direct path read would also be recorded as "physical reads".

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================================

On Wed, Nov 10, 2010 at 4:25 AM, Charlotte Hammond <
charlottejanehammond_at_yahoo.com> wrote:
Hi All,


For some of my sessions I see, for example:


V$SESS_IO shows 200,000 physical reads

V$SESSION_EVENT shows < 100,000 total waits for �db file * read� (and
�read by
other session�) etc.

Does that mean half my physical reads didn�t wait at all? How is that
possible? (I see this under high load - under low load number of reads is
approximately the same as the number of waits for the same SQL)


I'd be very grateful if you could explain this observation to me! (Platform
is
10g on AIX)

Thank you!

Charlotte




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