Differential files: their application to the maintenance of large data bases

ABSTRACT

The representation of a collection of data in terms of its differences from some pre-established point of reference is a basic compaction technique which finds wide applicability. This paper describes a differential database representation which is shown to be an efficient method for storing large and volatile databases. The technique confines database modifications to a relatively small area of physical storage and as a result offers two significant operational advantages. First, because the "reference point" for the database is inherently static, it can be simply and efficiently stored. Moreover, since all modifications to the database are physically localized, the process of backup and the process of recovery are relatively fast and inexpensive.