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. That allows the user to start small and grow the system. However, this shift in hardware also involves modification of software, including applications. A few vendors offer specialized software tools for data warehousing. Rudin recommends against using these special tools for a central, enterprise-wide data warehouse.