The five FSMO roles are:
- Schema master – Forest-wide and one per forest.
- Domain naming master – Forest-wide and one per forest.
- RID master – Domain-specific and one for each domain.
- PDC – PDC Emulator is domain-specific and one for each domain.
- Infrastructure master – Domain-specific and one for each domain.
In most cases an administrator can keep the FSMO role holders (all 5 of them) in the same spot (or actually, on the same DC) as has been configured by the Active Directory installation process. However, there are scenarios where an administrator would want to move one or more of the FSMO roles from the default holder DC to a different DC.
Moving the FSMO roles while both the original FSMO role holder and the future FSMO role holder are online and operational is called Transferring, and is described in the Transferring FSMO Roles article.
However, when the original FSMO role holder went offline or became non operational for a long period of time, the administrator might consider moving the FSMO role from the original, non-operational holder, to a different DC. The process of moving the FSMO role from a non-operational role holder to a different DC is called Seizing, and is described in this article.
If a DC holding a FSMO role fails, the best thing to do is to try and get the server online again. Since none of the FSMO roles are immediately critical (well, almost none, the loss of the PDC Emulator FSMO role might become a problem unless you fix it in a reasonable amount of time), so it is not a problem to them to be unavailable for hours or even days.
If a DC becomes unreliable, try to get it back on line, and transfer the FSMO roles to a reliable computer. Administrators should use extreme caution in seizing FSMO roles. This operation, in most cases, should be performed only if the original FSMO role owner will not be brought back into the environment. Only seize a FSMO role if absolutely necessary when the original role holder is not connected to the network.