A data warehouse is a “subject-oriented, integrated, timevarying,
non-volatile collection of data that is used primarily
in organizational decision making.”1 Typically, the data
warehouse is maintained separately from the organization’s
operational databases. There are many reasons for doing this.
The data warehouse supports on-line analytical processing
(OLAP), the functional and performance requirements of
which are quite different from those of the on-line transaction
processing (OLTP) applications traditionally supported by the
operational databases.