Backup Domain Controller. A Windows NT domain server that stores a backup of the database from the primary domain controller (PDC). The backup domain controller database is synchronized automatically with the copy of the database on the primary domain controller. A backup domain controller also authenticates users when they log on and can be promoted to a primary domain controller if necessary.
The backup domain controller (BDC) is a role that can be assigned to a server in a network of computers that use the Windows NT operating system. Windows NT uses the idea of a domain to manage access to a set of network resources (applications, printers, and so forth) for a group of users. The user need only to log in to the domain to gain access to the resources, which may be located on a number of different servers in the network. One server, known as the primary domain controller, manages the master user database for the domain. One or more other servers are designated as backup domain controllers. The primary domain controller periodically sends copies of the database to the backup domain controllers. A backup domain controller can step in as primary domain controller if the PDC server fails and can also help balance the workload if the network is busy enough.
Used on a Windows NT domain network. The BDC is designed to help the PDC in the authentication process and sharing the load on the network. There can exist an unlimited number of BDC's on a domain receiving a read only copy of the SAM Security Accounts Manager from the PDC every 5 minutes.
Backup Domain Controller. This is one or more computers running Windows NT that act as a backup to the primary domain controller. These machines can authenticate security requests just like the primary domain controller, and will take over for the PDC if it is not available. However, a BDC will remain a BDC until it is manually promoted to a PDC by a domain administrator.
Batch Data Communication. Used to define processing mode for a batch input sessions like Displaying all records, Displaying error dialogs, Process sessions in background etc.
backup domain controller. In Windows NT Server 4.0 or earlier, a computer running Windows NT Server that receives a copy of the domain's directory database (which contains all account and security policy information for the domain). The copy is synchronized periodically and automatically with the master copy on the primary domain controller (PDC). BDCs also authenticate user logon information and can be promoted to function as PDCs as needed. Multiple BDCs can exist in a domain. Windows NT 3.51 and 4.0 BDCs can participate in a Windows 2000 domain when the domain is configured in mixed mode. See also: primary domain controller (PDC)