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RE: Defragmenting a database

From: Thapliyal, Deepak <DThapliyal_at_ea.com>
Date: Wed, 11 Oct 2000 16:47:00 -0700
Message-Id: <10646.119028@fatcity.com>


sweeet .. i mean the explanation :)

-----Original Message-----
From: Gaja Krishna Vaidyanatha [mailto:gajav_at_yahoo.com] Sent: Wednesday, October 11, 2000 4:16 PM To: Multiple recipients of list ORACLE-L Subject: RE: Defragmenting a database

Vivek,

What I mean is that when the import is done, brand new blocks are allocated for the table and each block is filled upto PCTFREE, thereby utilizing each block to its maximum potential. Which means, if previously there were 10000 blocks with an average of 10 rows in each block, assuming that 100 rows can fit in 1 block, the new table after the import will contain 100 blocks. The result is that you have a much smaller table (decreased high water mark) and also any chained/migrated rows would be fixed (within reason). You are getting rid of both block-level and row-level fragmentation here.

The honeycombing effect I was referring to, usually relates to the "free space" in the datafile(s), but if you think about it, if a table has undergone multiple iterations of deletes and inserts, it is possible (based on its PCTUSED value),that honeycombing could occur even within a block.

Hope that helps,

Gaja


Gaja Krishna Vaidyanatha
Director, Storage Management Products, Quest Software Inc. Office : (972)-304-1170, E-mail : gajav_at_yahoo.com

Author - Oracle Tuning 101 by Osborne McGraw-Hill "Opinions and views expressed are my own and not of Quest"



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