A more realistic locking model and its analysis

摘要

The performance of transaction processing systems as affected by standard locking, i.e., the strict two-phase locking concurrency control method with the general waiting policy, has been reported in numerous studies based on analytic solutions and simulation. However, most studies assume a homogeneous database access model, i.e., all transactions follow the same access pattern of uniform or nonuniform database accesses. This paper is a major departure from previous works in that it considers a heterogeneous database access model, i.e., there are multiple transaction classes and accesses of each transaction class to the different regions of the database for different transaction steps is determined according to transaction's input parameters and the database state. The performance of the system is analyzed using an approximate low-cost iterative solution method, whose accuracy is ascertained by validation against simulation results. Numerical examples are provided to gain a better understanding of the implications of the model on the performance of transaction processing systems, with special attention being paid to the issue of detecting the onset of thrashing. The insights gained from this study should be useful in developing transaction scheduling methods to prevent thrashing.