Many iPlanet servers including Directory Server 5.1 use an instance of iPlanet Directory Server 5.1 to store configuration information. This information is stored in the o=NetscapeRoot directory tree. It does not need to be held on the same iPlanet Directory Server 5.1 as your directory data. Your configuration directory is the iPlanet Directory Server 5.1 that contains the o=NetscapeRoot.
If you are installing iPlanet Directory Server 5.1 only to support other iPlanet servers, then that iPlanet Directory Server 5.1 is your configuration directory. If you are installing iPlanet Directory Server 5.1 to use as part of a general directory service, then you will have multiple iPlanet Directory Server 5.1s installed in your enterprise and you must decide which one will host the configuration directory tree, o=NetscapeRoot. You must make this decision before you install any iPlanet servers (including iPlanet Directory Server 5.1).
For ease of upgrades, you should use a iPlanet Directory Server 5.1 instance that is dedicated to supporting the o=NetscapeRoot tree; this server instance should perform no other function with regard to managing your enterprise's directory data. Also, do not use port 389 for this server instance because doing so could prevent you from installing a iPlanet Directory Server 5.1 on that host that can be used for management of your enterprise's directory data.
Because the configuration directory normally experiences very little traffic, you can allow its server instance to coexist on a machine with another more heavily loaded iPlanet Directory Server 5.1 instance. However, for very large sites that are installing a large number of iPlanet servers, you may want to dedicate a low-end machine to the configuration directory so as to not hurt the performance of your other production servers. iPlanet server configurations result in write activities to the configuration directory. For large enough sites, this write activity could result in a short-term performance hit to your other directory activities.
Also, as with any directory configuration, consider replicating the configuration directory to increase availability and reliability. See the iPlanet Directory Server 5.1 Deployment Guide for information on using replication and DNS round robins to increase directory availability.
If the configuration directory tree if corrupted, you might need to reinstall all other iPlanet servers that are registered in that configuration directory. Remember the following guidelines when dealing with the configuration directory.
Always back up your configuration directory after you install a new iPlanet server
Never change the host name or port number used by the configuration directory
Never directly modify the configuration directory tree. Only the setup program for the various iPlanet servers should ever modify the configuration