Once users have jumped the hardware and software hurdles, some important implementation and management issues still stand in the way of building successful data warehouse applications. Rudin says the first challenge users typically face is justifying the expense of a data warehouse investment. These systems can cost hundreds of thousands of dollars, and the payoff isn't always clear-cut. Extraction, transformation and cleansing of data form a major challenge that must be met before the data warehouse becomes functional. Users have to establish the processes by which data from the operational systems get copied into the data warehouse.
Users have to make a lot of decisions up front about what the data means.
The information has to be translated into a common format before going into the data warehouse. Second, companies should build a data warehouse that will scale. It's not just the amount of data that increases rapidly, it's also the complexity of the queries and the number of users. Data begets data, and usage begets usage. The size of the database will double in a year to 18 months, and the number of users will increase by an order of magnitude.