This article applies to Domain Time.

Last updated: 5/23/2002

Problem

The Windows Time (W32Time) service turns itself back on, either after you have purposely set it to NoSync or have installed Domain Time II 2.5. Domain Time II 2.5 automatically sets the W32Time service to NoSync; earlier versions of Domain Time II simply disabled the W32Time service.

Details

If you have set the W32Time service to NoSync, it may switch back to NT5DS or NTP seemingly at random times.

The behavior is not random at all. It is a side-effect of running the NET TIME command from the command-line. The documentation for NET TIME /setsntp says this will clear the list of SNTP servers stored in the registry. It does indeed do this, but it also assumes you mean for the W32Time service to be set back to its default mode, which is NT5DS (that is, get the time from a domain controller using the Windows 2000 directory services to locate a time server).

When you run NET TIME /setsntp:server, the documentation says this will set the server(s) you supply as the SNTP time sources in the registry. While doing so, it also changes the mode to NTP, assuming you wouldn't be setting the sources if you didn't want to use them.

Background

The W32Time service may be set to one of three modes:
1. NT5DS -- use the Win2K method of locating a server, and use the NetRemoteTOD protocol for time
2. NTP -- use the servers you specify, and use the SNTP protocol
3. NoSync -- run, but don't check or set the time

On a Win2K Professional machine that is not a member of a Win2K domain, the service is disabled (that is, does not run at all). You may turn it on, but without also changing other parameters, you will only fill the event log with W32Time error messages. When you join a Win2K domain, the service is automatically enabled for you and set to NT5DS.

On a Win2K domain controller, the service is enabled by default, and set to use the NT5DS method (that is, get the time on at startup and periodically thereafter from the designated "inbound time partner" for that machine).

On the Win2K FSMO PDC (PDC emulator), the service is enabled by default, and administrators usually set it to use NTP instead of NT5DS. If using NTP, the FSMO PDC will get the time from the external time source the administrator specifies, and automatically pass it along to the machines using NT5DS elsewhere in the domain.

On Cluster Servers, either NT4 or Win2K, the W32Time service is enabled by default, and must remain running regardless of the mode (NT5DS, NTP, or NoSync) or else the event viewer will fill with error messages, and cluster failover may not work correctly.

If two time services are each trying to manage the clock, a "tug of war" may occur, with one service setting the time, then the other correcting the change, which triggers the first to correct again, and so forth in an annoying and unproductive loop. Aside from wasting CPU time and network bandwidth, the accuracy of the clock will suffer, sometimes dramatically.

When Domain Time version 2.5 or higher is installed, the W32Time service's mode is set to NoSync, but the service is left running. (Earlier versions of Domain Time disabled the service instead). With the service either disabled or set to NoSync, it will not interfere with Domain Time. On Cluster Server, it is important that the service stay running, even though it is not managing the clock. On other types of machines, it doesn't matter whether the service is disabled or just set to NoSync.

Solution

If you inadvertantly set the W32Time service to either NTP or NT5DS, you may either change it back to NoSync or (if it is not a Cluster Server) disable the Windows Time service. See Co-existing with Win2000 Time Service for instructions on editing the registry. Alternately, you may remove and reinstall Domain Time, which will make the necessary changes for you.