MDTF

Abstract

The Equal slack (EQS) heuristic is one of the widely used priority assignment heuristics. However, it severely suffers from the problems of intensive data contention, deadlock, and cyclic restart. To overcome some of the above problems, this chapter proposes a Most Dependent Transaction First (MDTF) priority heuristic that injects the size of dependent transactions of all directly competing transactions (that have requested access to the conflicting data item) in their priority computation. The MDTF heuristic efficiently reduces the data contentions among concurrently executing cohorts; and thus, it reduces the wastage of the system resources. This dynamic cohort priority assignment heuristic reduces the data contention considerably by utilizing the information about the dependency size of cohort(s). Doing this will make it easy for a currently executing cohort to better assess the level of data contention with absolutely no extra communication and time overhead. Such detailed dependency information is very useful to efficiently assign priorities to the cohorts.