Row Migration

From: Rahul <rahul.nimmagadda_at_gmail.com>
Date: Wed, 18 Jul 2007 16:21:04 -0000
Message-ID: <1184775664.057413.33100@i13g2000prf.googlegroups.com>

Hello all,

I have the following doubt regarding Row Migration. First let me explain my understanding of Row Migration -- When the space in a particular block is not sufficient to accommodate a row growing as a result of an update operation because of the low value of PCTFREE, results in Row Migration. Then the oracle server will move the entire row to a new block and leave a pointer from the original block to the new location. This results in the decrease of I/O performance.

My Query --
Instead of having a pointer from the original block to the new block, why doesn't oracle server delete the information about that particular row in the row directory slot of the original block and put the information about the row in the row directory slot of the new block as it is anyway moving the entire row to a new block. This can increase I/O performance as the number of I/Os required are less than the previous scenario.

Thanking you,
Rahul. Received on Wed Jul 18 2007 - 11:21:04 CDT