RE: Question about Dual

From: Connor McDonald <hamcdc_at_yahoo.co.uk>
Date: Sun, 12 Sep 2004 11:19:55 +0100 (BST)
Message-ID: <20040912101955.66278.qmail@web86904.mail.ukl.yahoo.com>

I'd guess its reduction in latching costs. There's no such thing as consistent read with x$ tables, so you don't need to latch them etc etc - you just go grab the data and you're done.

Interestingly, Oracle seem to have "given up" on people's predilection with unneccesarily querying from dual. In v10, there's a new optimization which skips the query to dual altogether.

Cheers
Connor

• ryan_gaffuri_at_comcast.net wrote:
  > does anyone know why x$dual has the reduce overhead? How is Oracle managing the memory
  > structure? Most x$tables incur serious performance problems. I would be hesitant to use it,
  > unless I knew more about what was going on internally.
  > -------------- Original message --------------
  >
  

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Connor McDonald
Co-author: "Mastering Oracle PL/SQL - Practical Solutions" ISBN: 1590592174 web: http://www.oracledba.co.uk
web: http://www.oaktable.net
email: connor_mcdonald_at_yahoo.com

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Received on Sun Sep 12 2004 - 05:15:26 CDT