Optimization Technology Study Of Multi-database System Transaction Processing

With the rapid development of network technology, a large number of data have emerged which stores in different forms in different systems, rather than gather points, gather and irregularities, with the status of distribute and heterogeneous. Although computers can be connected together physically easy by current technology, most systems run independently, making it cannot reach the purpose of sharing resources to each other. So, that how to obtain data to deal with from many distributed, heterogeneous data sources on different hardware platforms with the user-friendly manner becomes an urgent research topic. To solve the above problem need to build a multi-database system, whose core problem is the transaction process of multi-databases. This paper made the multi-database transaction process as the study object, and focused on the characteristics and relationship among global affairs, local affairs and global child affairs and studied how to keep the consistency of data in multi-database system.The main work done by this paper are as follows:(1) Studied using the strategy of transaction submission and ticket to keep the consistency of transaction in multi-database transaction module. By analyzing the global transaction manager scheduling algorithm TM1 and TM2 proposed by Mehrotra Et.Conclusion which use the transaction submission graph as the center, concluded that the shortcoming in TM1 and TM2 is that it cannot detect the indirect conflict between the global transaction and the local transaction, which is where the difficulty that ensure global serializability in the multi-databases environment is at.(2) To against the shortcoming mentioned above of TM1 and TM2, this paper proposed the algorithm TMO that is optimized from TM2, which increased the ticket strategy in order to increase data manipulation among each subtransaction in global transaction, making the potential conflict change into detective conflict, then solved the data nonconsistency problem caused by the inability to detect the potential conflict so that we achieved the purpose of maintaining the transaction serializability in multi-databases. Next, through adding savepoints to resume the suspended transaction instead of simply redoing it, it turned the completely rollback of related subtransaction into only partial rollback, which improved the execution efficiency of the system.(3) Finally, this paper described the framework of the multi-database system MBTMO, and gave the main design thought and the basic technology strategies used in MBTMO, such as schema integration, query processing, transaction processing, client program, etc., and integrated many databases. The MBTMO allows the User to use a global query language based on the SQL standard to access data in the local databases. Analyzed the advantages and disadvantages of MBTMO and pointed out the direction of future study.