A domain controller (DC) is a server that stores and manages information about the users, computers, and other resources in a Windows domain. DCs are responsible for authenticating users, authorizing access to resources, and replicating directory information to other DCs in the domain.
There are several ways to check the health and status of a domain controller. One way is to use the dcdiag command-line tool. Dcdiag can be used to check the following: