Optimal times of image copy for a multi-file database system

An image copy method has been used as the recovery mechanism for media failure in a general database system. However, this method spends high overhead costs for massive data transmission and much processing time in the normal operation of the database. To cover such weak points, an incremental backup method is adopted recently in most database systems. The incremental method is used before updated files reach a predetermined level, and on the other hand, the image copy method is done when they exceed this level. This paper considers the tradeoff between the overhead costs of the image copy and incremental backup methods, and discusses analytically and optimal policy for the incremental backup interval.