Chapter 16. Data Warehousing
A data warehouse is a repository of transaction and nontransaction data used for querying, reporting, and corporate decision making. The data typically come from multiple sources. They are not used for day-to-day corporate operations, and therefore once data have been stored, the data generally don't change as much as the databases we have used as examples up to this point.
Because of the cost associated with creating and maintaining a data warehouse, only very large organizations establish their own. Tables can grow to hold millions of rows; storage capacities have now moved into the petabyte range. Full-fledged data warehouses therefore require mainframe processing capabilities or clusters of smaller servers.