I wanted to ask about the fundamental differences between UNDO and REDO.
I read this thread
1397681 that started me off.
Then I read the rest and this is what I find:
UNDO contains before -image data, how the data existed before the change.
When the transaction is complete the undo segment is freed. UNDO is used to rollback transactions.
REDO records changes to the original data, and is important for transactions that are not committed at the time of a crash or failure. REDO is used to roll forward transactions.
Im sure there is more to add?
Thanks.