When should a differential backup be performed?

A differential backup is designed to capture all the changes made to the data since the last full backup. Therefore, it should be performed after a full backup has been completed. This practice ensures that the differential backup contains all the modifications that have occurred since the last full backup, making it easier to restore the data to the most recent state.

To clarify further, while performing differential backups on a daily schedule might seem practical, it's not a necessity as they only need to occur after a full backup. Similarly, performing them whenever data is modified significantly is not an effective strategy as it could lead to data consistency issues, particularly if multiple differential backups crowd together in close timeframes. Lastly, validating incremental backups is essential for ensuring data integrity, but it doesn’t directly influence the timing of when to perform a differential backup, which is specifically tied to the completion of the last full backup. Thus, the most accurate guideline for scheduling a differential backup is indeed the completion of a full backup.