CDS and GDA Server Processes
A CDS server stores and maintains object names within a cell and handles requests to create, modify, and look up data. One of the CDS server machines in a cell must be configured as a GDA server as well. There must be a GDA server (the gdad daemon) in a cell in order for the cell to communicate with other cells.
The following processes run on a CDS server machine:
· The CDS daemon, cdsd, is the CDS server process.
· The cdsadv on a DCE client machine, receives server advertisements to find out what servers are available. On a CDS server machine, it also sends server advertisements.
· The DCE control program (dcecp) for the management and maintenance of the CDS software. In addition, the cdscp program for controlling and displaying information about CDS clerks and servers. See DCE Administration Utilities for descriptions of these programs.
When preparing for CDS, you need to select server nodes that store and maintain the clearinghouses (CDS databases) in the cell. Keep the following guidelines in mind in order to achieve reliability, optimum performance, and data availability:
· Choose dependable nodes. A CDS server wants to avoid downtime as much as possible and needs to be restarted quickly when downtime occurs. The CDS server needs to be one of the first systems available on the network because client applications and other DCE servers rely on the CDS server for up-to-date information. The CDS server initializes the CDS namespace when you configure DCE.
· Use reliable network connections. This helps to ensure that all servers maintaining directory replicas can be reached when CDS performs a skulk. Skulks are periodic updates that check for consistency across all replicas.
· Consider the size of your cell and how geographically dispersed the cell is when deciding how many CDS servers you need. You should have at least two copies (one master and one replica) of each CDS directory to ensure access to data if one of the servers becomes unavailable.
· Each CDS server in a cell must maintain at least one clearinghouse. All clearinghouses should contain a copy of the root, in addition to other directories replicated there.
· Make replication decisions based on where the contents of directories are referenced. Put replicas where the contents are read and put masters where the contents are written.
In a DCE configuration that uses GDS or DNS, CDS must be able to contact at least one GDA to access global directory service. CDS contacts the GDA via the gdad daemon, which sends lookup requests for cell names to either GDS or DNS and returns the results to the CDS clerk in the cell that initiated the request.
The GDA can be on the same machine as a CDS server, or it can exist independently on another machine. You should have at least two gdad daemons running in a cell to ensure GDA availability.