Don't be a Pessimist: Use Snapshot based Concurrency Control for XML

Currently, only few XML data management systems support concurrent access to an XML document, and if they do, they typically apply variations of hierarchical locking to handle XML’s nested structure. However, advanced query processing techniques use a wide range of indexes and allow for arbitrary navigation through the XML documents, making lock acquisition complex and potentially leading to high blocking rates. In this paper, we suggest two concurrency control protocols that avoid any read locks by providing transactions a committed snapshot of the data. OptiX enhances traditional optimistic concurrency control to work on XML while SnaX offers snapshot isolation as provided by Oracle and PostgreSQL. We evaluate the performance of these two protocols on XML documents of different structure and on the XMark benchmark. For that purpose, we propose suitable update operations to serve as an extension to XMark which currently supports only queries.

• Type: Conference
• Year: 2006
• Where: ICDE
• Authors: Zeeshan Sardar, Bettina Kemme
• Keywords: Database, ICDE 2006, XML Data Management, XML Documents, XML’s Nested Structure