If there is a single key to survival in the 1990s and beyond, it is being able to analyze, plan and react to changing business conditions in a much more rapid fashion. To do this, top managers, analysts and knowledge workers in our enterprises need more and better information.

Information technology itself has made possible revolutions in the way that organizations today operate throughout the world. But the sad truth is that in many organizations despite the availability of more and more powerful computers on everyone's desks and communication networks that span the globe, large numbers of executives and decision makers can't get their hands on critical information that already exists in organization.

Every day organizations large and small create billions of bytes of data about all aspects of their business, millions of individual facts about their customers, products, operations and people. But for the most part, this data is locked up in a myriad of computer systems and is exceedingly difficult to get at. This phenomenon has been described as "data in jail".

Experts have estimated that only a small fraction of the data that is captured, processed and stored in the enterprise is actually available to executives and decision makers. While technologies for the manipulation and presentation of data has literally exploded, it is only recently that those involved in developing IT strategies for large enterprises have concluded that large segments of enterprise are "data poor."

1.2) Data Warehousing - Providing Data Access to the Enterprise

Recently, a set of significant new concepts and tools have evolved into a new technology that make it possible to attack the problem of provide all the key people within the enterprise with access to whatever level of information needed for the enterprise to survive and prosper in an increasingly competitive world.

The term that has come to characterize this new technology is "data warehousing". Data Warehousing has grown out of the repeated attempts on the part of various researchers and organizations to provide their organizations flexible, effective and efficient means of getting at the sets of data that have come to represent one of the organizations most critical and valuable assets. Data warehousing is a field that how grown out of integration of a number of different technologies and experiences over the last two decades. These experiences have allowed the IT industry to identify what are the key problems that have to be solved.

1.3) Operational vs. Informational Systems

Perhaps the most important concepts that has come out of the Data Warehouse movement is the recognition that there are two fundamentally different types of information systems in all organizations: operational systems and informational systems.

"Operational systems" are just what their name implies, they are the systems that help us run the enterprise operate day-to-day. These are the backbone systems of any enterprise, our "order entry', "inventory", "manufacturing", "payroll" and "accounting" systems. Because of their importance to the organization, operational systems were almost always the first parts of the enterprise to be computerized. Over the years, these operational systems have been extended and rewritten, enhanced and maintained to the point that they are completely integrated into the organization. Indeed, most large organizations around the world today couldn't operate without their operational systems and that data that these systems maintain.

On the other hand, there are other functions that go on within the enterprise that have to do with planning, forecasting and managing the organization. These functions are also critical to the survival of the organization, especially in our current fast paced world. Functions like "marketing planning", "engineering planning" and "financial analysis" also require information systems to support them. But these functions are different from operational ones, and the types of systems and information required are also different. The knowledge-based functions are informational systems.

"Informational systems" have to do with analyzing data and making decisions, often major decisions about how the enterprise will operate, now and in the future. And not only do informational systems have a different focus from operational ones, they often have a different scope. Where operational data needs are normally focused upon a single area, informational data needs often span a number of different areas and need large amounts of related operational data.

In the last few years, Data Warehousing has grown rapidly from a set of related ideas into an architecture for data delivery for enterprise end user computing.