Since its nationwide launch of RIM in August, about 1,000 GM dealers are active on the new system, and another 3,500 are enrolled and will soon be active.

According to Donna Colorito, process information officer at GM Service and Parts Operations, GM uses BEA Systems Inc.'s WebLogic Server to distribute parts information from its legacy systems and has adopted Electronic Business XML (ebXML) as its communications protocol. The RIM system also requires interfaces built into the dealer management systems.

There are some 28 vendors of dealer management systems. But the six largest, whose customers include about 85 percent of the North American dealerships, have completed the RIM integration, said GM officials. They include The Reynolds and Reynolds Co. in Kettering, Ohio, and Automatic Data Processing Inc. in Roseland, N.J.

A key aspect of the system is recommending what part to stock, and that's not a trivial thing. GM has some 1.3 million parts that can be ordered, and dealerships typically have between 5,000 and 12,000 parts on the shelf at any given time, said Mike Nicholes, a parts management consultant and head of Nicholes Capital Management LLC in Portland, Ore.

Ordering misjudgments can leave a dealer without a needed part or carrying a part that isn't used often. RIM recommends restocking policies for particular parts, and once the dealer agrees to that recommendation, the system automates the process of filling the orders on a daily basis.