Originally posted by farrokhp
Julian , you mean that if I multiply number of undo blocks by my block size I will get the Trans size ?
Yes, the no. of undo blocks used by the transaction.

is it for each trans or for a time period? Can I get the size from Rollbvack activity ? It's not clear for me yet!!
V_$TRANSACTION gives you a row for a transaction, while V_$UNDOSTAT (the one I use) gives you a new row every 10' in such a way that it keeps info only for the past 24 hours. It is a very good and useful view. But in 9i, with AUM, we don't bother anymore so much about RBSs. I don't use RBSs in 9i.