Domain Controller Diagnostic Tool DCdiagexe ST
This utility, as a matter of fact, is a complex test (or more precisely — a set of specialized tests) that allows an administrator to give a DC a quick "check up" and locate any possible problems. DCdiag verifies the serviceability of a DC as well as its relations (connectivity, trusts, replication issues, etc.) with other DCs that are the replication partners of the selected DC. Thus, the utility primarily checks up parts of Active Directory at a functional rather than a logical level (i.e., aspects such as data consistency, semantic contents, etc., are not affected).
It would be a good idea to run DCdiag after and even before (see the description of the DcPromo and RegisterInDns tests in Chapter 5, "Installing Active Directory") installation of domain controllers. It is fairly typical — especially in small networks — for an administrator to successfully (in his or her opinion) install Active Directory on the first DC and consequently believe that the domain will automatically work correctly since no faults were detected or error messages received. Problems usually begin when the administrator adds clients to the domain or installs a second DC (in the same or a different domain). Apparently, the first (root forest) DC was configured incorrectly; very often this concerns DNS service (on a Windows 2000/.NET Server or a third-party server). In such a situation, DCdiag (especially in conjunction with Net-Diag.exe) could locate many potential problems from the beginning.
The DCdiag utility can generate a very generous output — most of all, with enterprise-wide tests, and you should therefore use log files for subsequent analysis of the results. The diagnostic messages are quite informative and very often plainly specify a problem, so you need only eliminate it without any further analysis.
The Windows .NET version of DCdiag is sufficiently documented. You can use the built-in Help (dcdiag /?) as a quick reference on all parameters. (The built-in Help seems to be more accurate than Support Tools Help.) The Windows 2000 Server Resource Kit contains a great deal more information on how to use this utility. We shall discuss some of the most interesting features of DCdiag and examples of their use.
Note For the Windows 2000 environment, it is recommended that you download the updated version of DCdiag from
http://www.microsoft.com/downloads/release.asp?ReleaseID=22939.
You can run DCdiag from any network computer and test any DC in the forest. Some tests can be performed under a normal user account (Replications, NetLogons, and ObjectsReplicated cannot), but to get the full functionality of DCdiag, you must either be logged on as an administrator (or even as an enterprise administrator) or provide an administrator's credentials with the command.
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