What is a Data Warehouse?
One of the most important assets of any organization is its
information. This asset is almost always kept by an organization in two forms:
the operational systems of record and the data warehouse. The operational systems
are where the data is put in, and the data warehouse is where we get the data
out.
In an operational system users takes
orders, sign up new customers, and log complaints. They almost always deal with
one record at a time in an operational system. They repeatedly perform the same
operational tasks over and over. On the other hand, the users of a data warehouse watch the
wheels of the organization turn. They count the new orders and compare them
with last week's orders and ask why the new customers signed up and what the
customers complained about. Users of a data warehouse almost never deal with
one row at a time. Rather, their questions often require that hundreds or
thousands of rows be searched and compressed into an answer set. To further
complicate matters, users of a data warehouse continuously change the kinds of
questions they ask.
A data warehouse is a central
repository for all or significant parts of the data that an enterprise's
various business systems collect. Typically, a data warehouse is
housed on an enterprise mainframe server. Data from various online transaction processing
(OLTP) applications and other sources is selectively extracted and organized on
the data warehouse database for use by analytical applications and user queries.