Online Redefinition - FK on vs. FK off
- From: Freeman Robert - IL <FREEMANR@xxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx '" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 9 Mar 2004 12:29:16 -0600
An interesting issue has shown up in some redefinitions I'm doing in 9i
using the Online Redefinition features of Oracle. I'm wondering if anyone
has any insight into this.
I'm redefining a very LARGE LARGE table. This table has a number of FK
constraints to other tables. If I redefine the table, and create the FK's on
the interim table and leave then active, the redefinition process consumes
some 18GB of undo. However, if I disable the constraints, the process
consumes almost NO undo, and completes successfully.
While I expected the constraints would result in a great deal of recursive
SQL which would slow the process down, I'm shocked at the amount of undo
that is being generated with then enabled as opposed to when they are off.
Anyone have any thoughts on why this might be?
Robert
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