OSF DCE Administration Guide--Core Components

Chapter 22. Managing Intercell Naming
To find names outside of the local cell, CDS clerks must have a way to locate directory
servers in other cells. The Global Directory Agent (GDA) enables intercell
communications by serving as a connection to other cells through the global naming
environment. This chapter describes how the GDA works and how to manage it. The
chapter also describes how to define the local cell in either of the global naming
environments (GDS or DNS), which is a step that is necessary to make the local cell
accessible to other cells.
22.1 How the Global Directory Agent Works
The GDA is an intermediary between CDS clerks in the local cell and CDS servers in
other cells. A CDS clerk treats the GDA like any other name server, passing it name
lookup requests. However, the GDA provides the clerk with only one specific service; it
looks up a cell name in the GDS or DNS namespace and returns the results to the clerk.
The clerk then uses those results to contact a CDS server in the foreign cell.
A GDA must exist inside any cell that wants to communicate with other cells. It can be
on the same system as a CDS server, or it can exist independently on another system.
You can configure more than one GDA in a cell for increased availability and reliability.
Like a CDS server, a GDA is a principal and must authenticate itself to clerks.
CDS finds a GDA by reading address information that is stored in the
CDS_GDAPointers attribute associated with the cell root directory. Whenever a GDA
process starts, it creates a new entry or updates an existing entry in the
CDS_GDAPointers attribute. The entry contains the address of the host on which the
GDA is currently running. If multiple GDAs exist in a cell, they each create and
maintain their own address information in the CDS_GDAPointers attribute.
When a CDS server receives a request for a name that is not in the local cell, the server
examines the CDS_GDAPointers attribute of the cell root directory to find the location
of one or more GDAs. Figure 22-1 shows how a CDS clerk and CDS server interact to
find a GDA.
Figure 22-1. How the CDS Clerk Finds a GDA
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