There are some special considerations when building mixed LAN Manager and Microsoft Windows NT domains. As stated earlier, the Microsoft Windows NT Server computer must be the PDC in the domain. The user security information is replicated on the LAN Manager servers, and they can continue to validate user logons. However, the LAN Manager does not support the concept of local groups, only global groups. Thus, any local group definitions defined in the Microsoft Windows NT Server computer will be lost when replicated to the LAN Manager servers.