International Journal of Computer Theory and Engineering

Abstract

This paper proposes several timestamp ordering mechanisms for controlling concurrency in which the timestamps assigned to transactions can be modified dynamically during execution. These timestamps are not stored with the (database) variables and the process of modifying them is simple. The proposed mechanisms achieve a higher level of concurrency (than traditional timestamp ordering mechanisms) for the following reasons. First, the operations of (certain classes of) read-only transactions can always be accepted. Second, when an operation by an update transaction arrives out of order, the mechanism avoids rejecting it by modifying, if possible, the timestamps of some transactions. The proposed mechanisms do not require multiversion of each entity to be maintained.