undo_retention setting

[bookouri]

is there a "formula" to determine the best undo_retention setting for a database? This is my first experience with 9i and I havnt found much of help to make the transition to the auto undo stuff.

thanks

 

[ngibbs]

Not really as undo_retention is only a target. However, the value for UR will be useful in calculating the size of your undo using the formula (UR*Block_size* undo blocks per second) + block size. Basically you want to size your undo so that the before image is found in the undo if it is required for read consistency or whatever.