Business Users needed to build queries that summarized the data and fed management reports. Such queries, were extremely slow because they usually summarize large amounts of data, while sharing the database engine with every day operations,

Reason1

which in turn adversely affected the performance of operational systems.

Reason2

Delay in strategic planning of the enterprise.

The solution was, therefore, to separate the data used for reporting and decision

making from the operational systems. Hence, data warehouses were designed and built to house this kind of data so that it can be used later in the strategic planning of the enterprise.