Distributed Transaction Coordinator enables multiple copies of a specified file in two or more locations(databases) to automatically update/synchronize and be the same. (example -bank deposit is credited across all bank servers) Distributed Transaction Coordinator is a COM+ service, able to handle much more complex senarios then the simple deposit example, and may be active when Microsoft SQL Server or Personal Web Server is running. Commen Object Model (COM) -provides an interface for various programs to interact with commen objects(system resources). (COM+) -Similar to COM but with added features like more management capabilities.