Performance Characteristics of Epsilon Serializability with Hierarchical Inconsistency Bounds

Epsilon serializability (ESR) is a weaker form of correct-ness designed to provide more concurrency than classic serializability (SR) by allowing, for example, query transactions to view inconsistent data in a controlled fashion, by limiting the inconsistency within the speciied bounds. In this paper, we introduce the notion of hierarchical inconsistency bounds that allows inconsistency to be speci-ed at diierent granularities | with transactions being at the top of the hierarchy, objects at the bottom, and groups in between. We discuss mechanisms needed to control the inconsistency so that it lies within the speciied bounds. This paper also reports on an evaluation of the performance improvement due to ESR. We make two important observations. First, the thrashing point shifts to a higher multiprogramming level when transaction inconsistency bounds are increased. Further, for a particular multiprogramming level and a particular transaction inconsistency bound, the throughput does not increase with increasing object inconsistency bounds but peaks at some intermediate value.