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RE: (looong) PCTFREE, PCTUSED and ASSM

From: Khedr, Waleed <Waleed.Khedr_at_FMR.COM>
Date: Wed, 12 Nov 2003 06:34:40 -0800
Message-ID: <F001.005D66CF.20031112063440@fatcity.com>


I believe it's direct read from files in parallel execution, nothing gets read from cache.

Cached blocks for the table get flushed to files before the direct read.

Regards,

Waleed

-----Original Message-----
Sent: Wednesday, November 12, 2003 7:10 AM To: Multiple recipients of list ORACLE-L

Yep, the situation can get bad for parallel execution, especially if blocks read aren't cached...
But for serial FTS I haven't seen such a problem, I did even a test to verify it on 9.2.0.4, and did see behaviour as I expected - all blocks were scanned using multiblock reads and rows were returned in order the contents of them were found, instead of pointers.

Tanel.

> Actually row migration is a big problem for FTS also(whether serially or
> using PQ).
> You end up waiting for too many "db file sequential read" single block
reads
> instead of
> MBRC in (direct path read, db file scattered read)
>
> Regards,
>
> Waleed
>

-- 
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-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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Received on Wed Nov 12 2003 - 08:34:40 CST

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