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Re: Number of Transaction Slots

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 14 Mar 2002 18:18:26 -0800
Message-ID: <F001.0042A498.20020314181826@fatcity.com>

Taking a different tack - it doesn't really matter very much what the maximum is, as you don't want to have more than 5 concurrent transactions per rollback segment or you start losing space in rollback blocks in a big way. (There is a block reuse pool limited to 5 blocks). And you start getting contention on the segment header undo block if the concurrency goes too high.

Using a formula instead of just looking is perhaps a bit pointless - minor details can change over time, rapidly making the formula incorrect. As the economist said:

    "Yes, I know it works in practice, but does     it work in theory."

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 07 March 2002 21:25

|
|Thanks Robert, and thanks once again, Gopal.
|
|Now, metalink also has a formula for finding the number of
transaction
|slots (DOC ID: 177926.999), and Steve Adams too explains precisely
how he
|arrived at that number of 21 slots for a 2K block size at
|http://www.ixora.com.au/q+a/0008/29204045.htm without dumping the
header
|block, from v$TYPE_SIZE.
|
|But then the metalink has one formula, if the rollback segment has a
fixed
|number of extents, and another if it has unlimited number of extents.
Steve
|Adams also does refer to the extent control headers, but I think he's
done
|either of the one assumptions.

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Author: Jonathan Lewis
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Received on Thu Mar 14 2002 - 20:18:26 CST

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