Which statement is not correct?

a. Disk mirroring is a (near) real-time approach that writes the same data simultaneously to two or more physical disks.

b. Archiving is an approach in which database files are copied periodically to other storage media, such as tape or (another) hard disk.

c. Traditional relational databases allow for a certain measure of temporary inconsistency, in return for increased performance.

d. There is a tradeoff between the cost (overhead and storage cost) of more frequent backups and the cost of lost data because of less frequent backups.