Re: consistent reads and unique key updates

From: Ls Cheng <exriscer_at_gmail.com>
Date: Wed, 25 Apr 2012 21:40:45 +0200
Message-ID: <CAJ2-Qb8K33XZkpLG0h5dr0WcRn-EOcCa2xzpO6u=8-=AuATfLg_at_mail.gmail.com>

aha, let me check the book and rerun the test, I havent finished reading yet :-)
Thanks for the hint

On Wed, Apr 25, 2012 at 2:51 PM, Sidney Chen <huanshengchen_at_gmail.com>wrote:

> 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--
>
> --
> Regards
> Sidney Chen
>
>
>

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Received on Wed Apr 25 2012 - 14:40:45 CDT