## Using the DCE Directory Service

The DCE Directory Service can be used in many ways. It is used by the DCE services themselves to support the DCE environment. For example, cells are registered in the global part of the directory service, enabling users from different cells to share information and resources.

The directory service is also useful to DCE applications. The client and server sides of an application can use it to find each other's locations. The directory service can also be used to store information that must be made available in a globally accessible, well-known place.

For example, one DCE application could be a print service consisting of a client side application that makes requests for jobs to be printed, and a server side that prints jobs on an available printer. The directory service could be used as a central place where the print clients could look up the location of a print server. It could also be used to store information about printers; for example, what type of jobs a printer can accept and whether it is currently up or down and lightly or heavily loaded.

In some ways, a directory service can be used in the same way as a file system has traditionally been used; that is, for containing globally accessible information in a well-known place. An example is the use of configuration information stored in files in a UNIX /etc directory.

However, the directory service differs in important ways. It can be replicated so that information is available even if one server goes down. Replicas can be kept automatically up-to-date, so that, unlike multiple copies of a file on different machines, the information in the replicas of the directory service can be kept current without manual intervention.

The directory service can also provide security for data that is kept in a globally accessible place. It supports access control lists (ACLs) that provide fine-grained control over who is able to read, modify, create, and perform other operations on its data.

As you learn about the directory service and how to access it, think about the ways in which your application can best take advantage of the services it provides.

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