RE: db file sequential read [WAS:wait event puzzler]

KG,

What are the scenarios other than index scans when a single block read can happen (>8i as you said) and hence "db file sequential read" be reported?

Regards
Naveen
> -----Original Message-----
> From: K Gopalakrishnan [mailto:[EMAIL PROTECTED]
> Sent: Thursday, June 12, 2003 1:54 PM
> To: Multiple recipients of list ORACLE-L
> Subject: RE: db file sequential read [WAS:wait event puzzler]
>
>
> Mladen:
>
> Prior to 8i (or 8) you see the multiblock sequential reads while doing
> the reads from the sort segments or temporary segments. But in 8i sort
> IO is done as direct IO and we see some other waits.
>
> Starting from 8i the db file sequential read is always a single block
> read which TYPICALLY happens during index scans..
>
> Are you convinced?
>
> Best Regards,
> K Gopalakrishnan
>
>
> --- "Gogala, Mladen" <[EMAIL PROTECTED]> wrote:
> > A SINGLE block? I was convinced that it was <=
> > DB_FILE_MULTIBLOCK_READ_COUNT
> > blocks.
> > Are you sure?
> >
> > Mladen Gogala
> > Oracle DBA
> > Phone:(203) 459-6855
> > Email:[EMAIL PROTECTED]
> >
> >
> > -----Original Message-----
> > Sent: Wednesday, June 11, 2003 2:19 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Dennis:
> >
> > THe event 'db file sequential read' is NOT always an INDEX Scan. It
> > is
> > just a single block read which TYPICALLY happens during an INDEX
> > scan.
> > The word 'TYPICALLY' is the key here.
> >
> >
> >
> > Best Regards,
> > K Gopalakrishnan
> >
> >
> >
> >
> > -----Original Message-----
> > Meng, Dennis
> > Sent: Wednesday, June 11, 2003 11:02 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Good day all,
> > We have a bunch of queries in our data warehouse
> environment that are
> > taking
> > a long time to complete.
> > I did a select on v$session_wait on one of the queries when it is
> > running
> > and it shows the wait event to be 'db file sequential read', which
> > means it
> > is scanning index blocks, correct? But when I put the p1 p2 p3
> > values into
> > another query to see which segment it belongs to, it shows me a
> > table, not
> > an index. How can this be?
> >
> >
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: K Gopalakrishnan
> INET: [EMAIL PROTECTED]
>
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Author: Naveen Nahata
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