When a user logs on, %LOGONSERVER% is defined and set to the name of the authenticated computer. It is not propagated to a user's environment variables prior to NT 4.0 SP3. Therefore, you cannot use the %LOGONSERVER% environment variable in logon scripts before NT 4.0 SP3. For example, if the user's profile path is %logonserver%\profiles\user1.man and the name of the authenticating server is MYSERVER, the user profile path is set to \\MYSERVER\profiles\user1.man. Therefore, if you maintain a copy of the user profiles on each domain controller, users can access their user profiles when the primary domain controller is unavailable. %LOGONSERVER% is an undocumented environment variable.
When you specify a path statement for the user profile path, the following entry in User Manager is valid:
%logonserver%\<share name>\<profile>.<usr or man>
NOTE: To simplify the maintenance of user profiles on multiple servers, use Directory Replication to copy the user profiles from the primary domain controller (PDC) to the backup domain controllers (BDCs).
Roaming User Profiles Under Windows NT 4.0If you use %LOGONSERVER% with roaming user profiles under Windows NT 4.0, roaming user profiles are saved to the logon server (typically a BDC) when users log off. If the user is authenticated by different logon server the next time he or she logs on, a message appears indicating the local copy of the roaming user profile is newer than the copy on the logon server (assuming that the user logs on to the same computer). If the user logs on to a different computer, and is authenticated by a logon server that does not contain the latest copy of his or her roaming user profile, it appears to the user that his or her changes to the roaming user profile have been lost. This can cause confusion and increase internal support costs for companies using roaming user profiles.
For this reason, it is best to use %LOGONSERVER% with only mandatory user profiles, and not with roaming user profiles.