Overview

MS RPC and Cedar provide specialized services related specifically to the transport of invocations across the network. There are other services, however, that we might loosely think of as services that help in communication, but that are not part of either MS RPC or Cedar.

In this chapter we will look at these functions, what they do, and how they work.

Some are automatically provided for the developer by DCOM such as context bridging. Some are provided automatically but require developer involvement such as triggering, and some are services the developer can use to help him or her write component-based applications such as multicasting Where the developer is involved, however, all these services are accessed via the same COM interface.

Triggering

Components in DCOM can be running permanently in memory loaded and waiting to be used or they can be stored somewhere in a library. Where they are stored in a library, when a request is made for them, they need to be loaded into memory and started. This latter process is termed "triggering," and DCOM is able to trigger components.

The advantages of triggering are that if the developer has literally thousands of components to use on a machine, he or she can save memory by storing them on disk and only triggering them when needed. This aspect is especially useful if you only have a small machine it makes better use of the small amount of memory you may have available, while at the same time still providing a client process with...