Final answer:
Two types of log-based recovery are undo logging and redo logging.
Step-by-step explanation:
Two types of log-based recovery commonly used in database systems are undo logging and redo logging.
Undo logging involves logging the old values of the modified data items before they are updated. This allows for the undoing of transactions by reapplying the old values recorded in the log during recovery.
Redo logging involves logging the new values of the modified data items after they are updated. This allows for the redoing of transactions by reapplying the new values recorded in the log during recovery.