Parallelism and recovery in database systems

TLDR

Database recovery often requires maintaining two versions of an object—the new and the old—to ensure consistency. The paper proposes a new method to increase parallelism in database systems by enabling readers and writers to operate concurrently on the same object. The method introduces a scheme that allows simultaneous reader–writer access to an object, with several variations tailored to the desired level of parallelism. The authors prove that transactions following this scheme preserve consistency.

Abstract

In this paper a new method to increase parallelism in database systems is described. Use is made of the fact that for recovery reasons, we often have two values for one object in the database—the new one and the old one. Introduced and discussed in detail is a certain scheme by which readers and writers may work simultaneously on the same object. It is proved that transactions executed according to this scheme have the correct effect; i.e., consistency is preserved. Several variations of the basic scheme which are suitable depending on the degree of parallelism required, are described.