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
Next Seminar - UK, April 3rd - 5th
http://www.jlcomp.demon.co.uk/seminar.html
Host to The Co-Operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
Author of:
Practical Oracle 8i: Building Efficient Databases
-----Original Message-----
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
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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