RE: Buffer Sort explanation

From: Lex de Haan <lex.de.haan_at_naturaljoin.nl>
Date: Thu, 4 Aug 2005 10:47:06 +0200
Message-Id: <20050804084707.72A7D1DBBE6@turing.freelists.org>

a BUFFER SORT typically means that Oracle reads data blocks into private memory, because the block will be accessed multiple times in the context of the SQL statement execution. in other words, Oracle sacrifies some extra memory to reduce the overhead of accessing blocks multiple times in shared memory. this has nothing to do with sorting ...

additions/corrections welcome,
kind regards,

Lex.  

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-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Deepak Sharma
Sent: Wednesday, August 03, 2005 23:31
To: oracle-l_at_freelists.org
Subject: Buffer Sort explanation

What does the 'BUFFER SORT' step mean and how does it get calculated, say in below example? It is out of a tkprof output of a star transformation query.

    105      BITMAP MERGE
 351549        BITMAP KEY ITERATION
127009880       BUFFER SORT
1607720         TABLE ACCESS FULL SYS_TEMP_4254956840
 351549       BITMAP INDEX RANGE SCAN OBJ#(3441108)

PARTITION: 1 177 (object id 3441108)

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http://www.freelists.org/webpage/oracle-l Received on Thu Aug 04 2005 - 03:49:08 CDT