FAS - A Freshness-Sensitive Coordination Middleware for a Cluster of OLAP Components

Data warehouses offer a compromise between freshness of data and query evaluation times. However, a fixed preference ratio between these two variables is too undifferentiated. With our approach, clients submit a query together with an explicit freshness limit as a new Quality-of-Service parameter. Our architecture is a cluster of databases. The contribution of this article is the design, implementation, and evaluation of a coordination middleware. It schedules and routes updates and queries to cluster nodes, aiming at a high throughput of OLAP queries. The core of the middleware is a new protocol called FAS (FreshnessAware Scheduling) with the following qualitative characteristics: (1) The requested freshness limit of queries is always met, and (2) data accessed within a transaction is consistent, independent of its freshness. Our evaluation shows that FAS has the following nice properties: OLAP queryevaluation times are close (within 10%) to the ones of an idealistic setup with no up...

• Type: Journal
• Year: 2002
• Where: VLDB
• Authors: Uwe Röhm, Klemens Böhm, Hans-Jörg Schek, Heiko Schuldt
• Keywords: Database, Explicit Freshness Limit, Freshness Limit, Query Evaluation Times, VLDB 2002