Re: consistent reads and unique key updates

From: Sidney Chen <huanshengchen_at_gmail.com>
Date: Wed, 25 Apr 2012 20:51:16 +0800
Message-ID: <CAM_ddu-Kszx+Uq=Ap-RWA=atFWFJw2hsaX5YLFuH6Q1nEDQg7w_at_mail.gmail.com>

Quote from Jonathan Lewis's new book "Oracle Core", you can check the stats "RowCR attempts", "RowCR hits" in session 1 to confirm this.
--quote--

When Oracle accesses a row through an indexed access path, it may be able to use the RowCR (row consistent read) mechanism when it gets to the table block. This means that Oracle has gone through the complex processing I’ve just described to get the index leaf block into a read-consistent state and has then been able to check that the row itself has not changed since the reconstructed commit SCN for the index entry.

--end of quote--

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Regards
Sidney Chen

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http://www.freelists.org/webpage/oracle-l Received on Wed Apr 25 2012 - 07:51:16 CDT