Lightweight locking protocol for XML data management

Abstract

In the XML database management system for performance-critical transactions, a concurrency control scheme is mandatory to preserve consistent behavior and to provide reasonable performance. The transactions in the XML databases often access a large number of elements on the XML data hierarchy with multiple operations for the structure changes and data-value updates. In such transactions, using conventional concurrency control schemes could not achieve acceptable performance because they do not successfully deal with pseudo-conflict situations for insertion transactions. In this thesis, we propose a new concurrency control scheme, called lightweight locking (LWL), which allows repeatable retrievals without phantom problems from unrestricted insertion transactions on the data hierarchy in the XML database. In order to reduce pseudo-conflict cases among active transactions, the LWL is an improved scheme based on the multigranularity locking. For clearing up inconsistent-retrieval possibility by phantom phenomenon, the LWL also maintains the forged versions. To investigate the application areas of LWL, its performance has been evaluated by means of experimental simulation. In the experiment for diverse applications, the LWL scheme exhibits reasonable performance in comparison with relevant schemes despite having version management overheads.