DATA MARTS: FAST FOOD FOR DECISION SUPPORT GOURMETS
by Doug Laney, Consulting Manager, Prism Solutions

Data marts have become the information management Happy Meal. As a seemingly inexpensive, expeditious alternative to a data warehouse, the data mart has risen rapidly in popularity over the past year. While "cheap" and "fast" can be good, you should consider other factors in selecting which of these decision support architectures your business should consume.

The Virtual Warehouse Snack

By now the average IT professional is well aware that the "virtual data warehouse" architecture is like a diet of candy bars: It provides instant data access gratification, meager nutritional value, little substance, and may only taste good to the end user for the first few meals. Preparing a virtual data warehouse is as simple as opening the wrapper, but maintaining this kind of diet can make one starve for integrated, meaningful, historical, strategic information.

Many organizations believe the virtual data warehouse is a way to prototype a true data warehouse. True, slapping a data access tool on top of production databases will demonstrate access to operational data. But even this is only a functional prototype, i.e. pictures on the menu. The real challenge is to create a technical prototype - one that demonstrates the process and tools needed to really build a data warehouse. Nothing prepares an organization more for a data warehouse than actually following a real recipe and dirtying some pots, while producing a sample of the meal to come.

The Data Mart Drive-Through

The independent data mart is widely perceived as a panacea for businesses looking for a low-cost, rapid data warehouse-like solution. Yet, even prominent data mart solution vendors refer to them as "quick and dirty" tactical niche solutions that "may be short term (less than 2-3 years) with the intention of discarding them" and that data marts "skirt tough architectural issues." Think about it-isn't this the very same mentality that created a state of operational system "spider webs" that today require constant maintenance and frequent reengineering?

While an independent data mart may satisfy your immediate hunger for information, companies adopting them as a starting point for data warehousing may become fat, if not sick, on this strategy. Many companies think that they will grow their disparate data marts into an enterprise data warehouse. This can be just as difficult as eating a variety of fast-food to attain a well-balanced diet.

This is not to say that data marts are a half-baked idea when it comes to enterprise decision support. The dependent data mart concept has existed ever since Bill Inmon cooked-up the iterative, architected data warehousing approach. However, the data mart has been the ultimate level of analytical data, not the starting point. In forward thinking organizations, business solution-specific data stores (a.k.a. data marts) should grow from a common layer of granular strategic data (a.k.a. atomic data), not vice-versa. An enterprise approach that aims to blend together already-prepared independent data marts can yield redundant data extraction routines along with the usual complementary performance and inconsistency horrors.

Chez Data Warehouse

Just as a seven course gourmet meal is served one dish at a time, an enterprise data warehouse should be constructed one departmental solution at a time. Attempting to serve too many data dishes at once is a major reason enterprise data warehouse efforts tend to exceed schedule and budgets. This type of indigestion is what happens to end users when companies perform poor data warehouse meal planning and hire short-order cooks instead of highly-trained, experienced chefs.

Yes, it takes a strong knowledge of the multi-level data acquisition architecture and strong data warehouse project management skills to make this work. But the rewards of true data warehousing, as the IDC study pointed out, are very well worth it. So if you want a successful data warehouse, be a data gourmet, not a data gourmand. If you're planning to order meal-after-meal of a hamburger, french fries and shake, instead consider changing it to a single serving of filet mignon, pomme frites and a glass of champagne.

For more information, see http://www.prismsolutions.com