Partly-consistent cuts of databases

Abstract

We introduce partly-consistent cuts, a mechanism analogous to causal cuts, defined in the context of object-oriented databases. A partly-consistent cut is a collection containing one or more copies of every page in a given database; the copies are made during the operation of the database, at different times. We consider four classes of partly-consistent cuts. Each class implies a different set of constraints imposed on the times when the copies are made. The consistency properties (i.e. the ability to correctly represent what happens in the actual execution of the database) of the cuts in each class are analyzed. One class, called GC-consistent cuts, can be used by a concurrent garbage collector to determine which objects to delete.