Research On Distributed Concurrency Control Mechanism For XML Data

Abstract:XML has become a standard for data exchange in many fields of application. Thus, a huge amount of data in this format is spread around Web and is stored in different ways. Therefore it has become necessary to have efficient systems for managing these XML documents in a distributed environment. In order to manage the data, traditional DBMSs use distributed concurrency control protocols. However, the structure of XML data raises difficulties in the application of these protocols, affecting the level of concurrency in both centralized and distributed environments.For centralized environments, there is a large number of proposals for XML data concurrency control. As a result, there is a larger number of deadlocks,and use of a very limited subset of the XPath language, and them unfeasible for use in practical systems. Considering distributed environments, there are still few proposals, such as. These present a low level of concurrency, affecting response time. Also, there are no studies explicitly evaluating performance aspects.In order to provide effective management in distributed environments, this article DCCXML based on distributed transaction processing for XML was introduced as a concurrency control mechanism for distributed XML data. DCCXML protocol support it and any XML document storage method of communication; DCCXML employs the synchronous approach to execute transactions, using the locking technique. With this approach it is possible to assure the organization of messages between sites, as well as the exclusive access to shared resources. Response time was proposed to improve.It has low granularity. According to the transactional properties of consistency and isolation in the distributed scope, improving performance by means of a concurrent access to physically distributed data.By DCCXML was evaluated, considering its performances of response time and number of deadlocks. DCCXML obtained advantages that handle distributed concurrency control protocol for XML data. DCCXML improved response time in the execution time of distributed transactions in several situations. DCCXML is flexible, allowing adaptation of other concurrency control protocols, such as the one used in the evaluation.