Management, Design, Reliability

This paper proposes an effective Web services (WS) transaction management framework to automatically manage inconsistencies occurred by relaxing isolation of WS transactions. Categories and Subject Descriptor

Accelerating Database Processing at e-Commerce Sites

Abstract. Most e-commerce Web sites dynamically generate their contents through a three-tier server architecture composed of a Web server, an application server, and a database server. In such an architecture, the database server easily becomes a bottleneck to the overall performance. In this paper, we propose WDBAccel, a high-performance database server accelerator that significantly improves the throughput of the database processing, and thus that of the overall Web site. WDBAccel eliminates costly, complex query processing needed to obtain query results by reusing previous query results for subsequent queries. This differentiates WDBAccel from other database cache systems, which replicate a database into multiple conventional DBMS’s and distribute queries among them. We evaluate the performance of WDBAccel by using the queries of the TPC-W benchmark. The measurement results show that WDBAccel outperforms DBMS-based cache systems by up to an order of magnitude.

Maintaining Consistency Under Isolation Relaxation of Web Services Transactions

Abstract. For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web services operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transac-tions, which can spoil data integrity and causes incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transac-tions. The mechanism effectively detects inconsistent states of transactions with a notion of a completion dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy inte-gration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.

A Request Distribution Method for Clustered VOD Servers Considering Buffer Sharing Effects

The clustering of multiple video servers is a popular architecture for huge VOD systems. In a clustered VOD system, user requests are distributed among the video servers by the dispatcher. Each video server consists of independent disks and a local buffer memory. The buffer mechanism is recognized helpful to the improvement of the disk performance. However, its effects have not been effectively utilized so far for the request distribution strategies of the clustered VOD system. In this work, we investigate the effects of buffer sharing on the throughput of the clustered VOD system. And, based on the results, we propose a request distribution method for the clustered VOD system, where the buffer sharing effects are utilized for improving the system’s throughput. By experiments, we evaluate the performance of the proposed method compared with the conventional request distribution methods