Distributed Component Object Model

In addition to supporting component object model (COM) for interprocess communication on a local computer, Windows 2000 supports the distributed component object model (DCOM). DCOM is a system of software objects designed to be reusable and replaceable. Objects are software components that can perform and support applications. The objects support sets of related functions such as sorting, random-number generation, and database searches. Each set of functions is called an interface, and each DCOM object can have multiple interfaces. When applications access an object, they receive an indirect pointer to the interface functions. The pointer has information on the location of an object. After receiving this pointer, the calling application doesn't need to know where the object is or how it does its job since the pointer directs the calling application to it.

DCOM allows processes to be efficiently distributed to multiple computers so that the client and server components of an application can be placed in optimal locations on the network. Processing occurs transparently to the user because DCOM handles this function. Thus, the user can access and share information without needing to know where the application components are located. If the client and server components of an application are located on the same computer, DCOM can be used to transfer information between processes. DCOM is platform independent and supports any 32-bit application that is DCOM-aware.

Advantages of Using DCOM

DCOM is a preferred method for developers to use in writing client/server applications for Windows 2000. With DCOM, interfaces to software objects can be added or upgraded, so applications aren't forced to upgrade each time the software object changes. Objects are software entities that perform specific functions. These functions are implemented as dynamic-link libraries so that changes in the functions, including new interfaces or the way the function works, can be made without rewriting and recompiling the applications that call them.

Windows 2000 supports DCOM by making the implementation of application pointers transparent to the application and the object. Only the operating system needs to know if the function called is handled in the same process or across the network. This frees the application from concerns with local or remote procedure calls. Administrators can choose to run DCOM applications on local or remote computers, and can change the configuration for efficient load balancing.

Your application might support its own set of DCOM features. For more information about configuring your application to use DCOM, see your application's documentation.

DCOM builds upon remote procedure call (RPC) technology by providing an easy-to-use mechanism for integrating distributed applications on a network. A distributed application consists of multiple processes that cooperate to accomplish a single task. Unlike other interprocess communication (IPC) mechanisms, DCOM gives you a high degree of control over security features, such as permissions and domain authentication. It can also be used to start applications on other computers or to integrate Web browser applications that run on the Microsoft® ActiveX® platform.