parallellism plays a significant role in processing massive databases. Teradata pioneered some of the sky technology. All major vendors of databases management systems now offer data partitioning and parallel query proceseeing technology. The article by Dewitt and Gray provides an overview of this area28. One interesting technique relevant to read-only environment of decision support systems is that of piggybacking scans requested by multiple queries used in Redbrick. Piggybacking scan reduces the total work as well as response time by overlapping scans of multiple concurrent requests.