ASGT: An Approach to Concurrency Control in Mobile Transaction Management Based on Prediction and Adaptation

Mobile transaction management is one of the most important fields in the research of mobile database. Though disconnection will never be a main problem in the high quality of wireless network nowadays, the high instability of bandwidth still produces a larger fluctuation of transaction executing time which leads to a higher blocking rate. Furthermore, due to high density of MUs, the database server will work under a high workload circumstance and meet the thrashing in a larger probability. A new scheme, called ASGT (active serialization graph technique), is developed to overcome these problems. In the ASGT, reading never blocks writing, thus it can substantially reduce the blocking rate. The ASGT can detect and break some non-serializable scheduling in advance, which can greatly shorten the suspending time of transactions involved. Due to an explicit serializable sequence maintained in running time, the scheduler, integrating an aborting method called MWDL, can improve the throughput and reduce the scheduling cost. The theoretical analysis and execution of a simulation based on C++SIM show that the performance of the ASGT overmatches an improved 2PL in most conditions of a mobile environment.