Data Warehouses

• Consolidate data from many sources in one large repository
• Loading, periodic synchronization of replicas

Common architecture

• Databases at branches handle OLTP queries
• Local store databases copied to a central warehouse overnight
• Analysts use the warehouse for OLAP and data mining

Warehousing Challenges

• Semantic integration: Eliminate mismatches when integrating data from multiple sources
• Heterogenous sources: Must fit the schemas of different sources together
• Load, Refresh, Purge: Must load data, periodically refresh it, and then purge old data
• Metadata Management: Must keep track of source, loading time, and other information