Research On A Few Key Issues Of Mobile Transaction Management

Mobile database is one of the hottest fields in computer science. Being the infrastructural technology, mobile transaction management should be in charge of high-efficient and consistent access to database under the compact of mobile environments, such as the instability of wireless channel and the mobility of Mobile Units.This paper proposed the achievements made in a few key research fields of mobile transaction management-local transaction management, intra-transaction concurrency control and global commitment of mobile units.Firstly, an approach, called ASGT, to concurrency control of local transactions in a high-quality Centralized mobile environment is proposed. The high-quality mobile environment fulfills the usability of traditional block-based method of concurrency control, however, this will result in a high blocking rate due to bandwidth fluctuating of wireless communications. Possessed an outstanding low blocking property, ASGT can substantially improve the concurrency, throughput and trashing of mobile transaction, and still confirms the strict consistency. A new schema, called Afterward Validating, is introduced into ASGT to predict the future conflicts and abort the corresponding transaction in advance. ASGT, with the same computational complexity of scheduling cost as 2PL, can produce a remarkable performance. We demonstrate the efficiency of ASGT by both analytic model and simulation results.And then, a variation of ASGT, called TASGT, shortened by TASGT, is proposed to survive the impact of complex structures on mobile transaction processing. The scheduling of ASGT in a transaction with complex structures may lead to the misaborting a transaction for the predication manner of Forward Validating. TASGT can avoid the misaborting by pruning the overlooked branches dynamically during processing of transactions.Thirdly, We introduce the intra-transaction method traditionally used in the fields of static or parallel transaction management into the management of Kangaroo transaction model. Being one of the most applicable mobile transaction models, Kangaroo is heavily impacted by the serial manner of sub-transaction processing. An approach, called IKCC (Intra-Kangaroo Concurrency Control) is introduced to implement the intra-transaction scheduling in a Kangaroo Transaction. Based on a static 2PL, IKCC can take full advantage of non-strict manner in intra-transactionaccessing and produce the validated scheduling history dynamically by Splitting, Propagating and Merging Steps.Lastly, An atomic committing protocol, called 2 Layer 2PC(2L2PC), is developed to survive the mobile units from instability and inefficiency in global commit by combining the commit protocol of fixed layer with that of mobile layer. Based on a Presumed Commit 2PC (PrC), 2L2PC can make the most of the underlying commit protocol and the stability of fixed nodes to initiating the commit concurrently from both two layers, hence it can save a Force Write Log and a round of messages, which can remarkably improve the time complexity of commit process. 2L2PC can free the global coordinator in advance to amending the inherent defect of PrC in aborting cases. If the handoff phenomenon takes place during the committing, 2L2PC can avoid tracking the handoff path in a large degree by deleting the HOP-IN/HOP-OUT pares of information and executing a Matching Algorithm in global decision, which can efficiently smooth the cost of handling the handoff. According to the general measurement of commit cost, the efficiency of 2L2PC is shown by comparing to an existed commit protocol in mobile environment, and the efficiency of handoff processing in 2L2PC is also demonstrated by comparing to the existed approaches.