Performance analysis of dynamic finite versioning for concurrent transaction and query processing

Abstract

In this paper, we analyze the performance of dynamic finite versioning (DFV) schemes for concurrent transaction and query processing, where a finite number of consistent snapshots can be derived for query access. We develop analytical models based on a renewal process approximation to evaluate the performance of DFV using M ≥ 2 snapshots. The storage overhead and obsolescence faced by queries are measured. Simulation is used to validate the analytical models and to evaluate the trade-offs between various starategies for advancing snapshots when M > 2. The results show that (1) the analytical models match closely with simulation; 2) both the storage overhead and obsolescence are sensitive to the snapshot-advancing strategies, especially for M > 2 snapshots; and (3) generally speaking, increasing the number of snapshots demonstrates a trade-off between storage overhead and query obsolescence. For cases with skewed access or low update rates, a moderate increase in the number of snapshots beyond 2 can substantially reduce the obsolescence, while the storage overhead may increase only slightly, or even decrease in some cases. Moreover, for very low update rates, a large number of snapshots demonstrates a trade-off between storage overhead and query obsolescence. For cases with skewed access or low update rates, a moderate increase in the number of snapshots beyond 2 can substantially reduce the obsolescence, while the storage overhead may increase only slightly, or even decrease in some cases. Moreover, for very low update rates, a large number of snapshots can be used to reduce the obsolescence to almost zero without increasing the storage overhead.