Instance Recovery Have 2 stages:
-Roll Forward (Recover commited and uncommited transaction in buffer cache and restore undo data to undo tablespace)
-Roll Backward(rollback all uncommited transaction in database)
my question is : does oracle restore undo block if the undo block still exist in undo tablespace. or oracle only restore overwritten undo block in undo space? because from what i know data in undo tablespace still exist even after shutdown.