A method for performing data backups is disclosed. An initial backup
operation is performed on all datasets within a recording medium. A
subsequent backup operation is performed on any of the datasets in a day
at which the dataset has been rewritten or in a day at which a
predetermined period for the dataset expires, whichever day comes first.
The subsequent backup operation is performed on any of the datasets until
another initial backup operation needs to be performed on all of the
datasets again.