When the .NET client application is running on the same machine as the Data Access Server (DAS), and DBMS authentication is not enabled, the .NET Data Provider does not require a user ID and password to establish a DBMS connection. The .NET client process user ID is used to establish the connection when a user ID and password are not provided.

If DBMS authentication is enabled and the user password is required, then the user ID and password must be provided even if the connection is to the same machine.

If the target database name specification includes a VNODE name specification, the VNODE login information is used to access the DBMS machine. Optionally, a user ID and password can be provided and is handled as described next.

When the DAS and DBMS servers are on different machines, a VNODE name is required in the target database specification of the form vnodename::dbname. The VNODE provides the connection and (optionally) login information needed to establish the DBMS connection.

The connection string keyword Vnode_usage determines how the VNODE is used to access the DBMS. Vnode_usage also determines the context (DAS or DBMS) in which the application user ID/password is used. If the target database specification does not contain a VNODE name, the Vnode_usage specification is ignored.

When Vnode_usage is set to CONNECT, only global VNODE connection information is used to establish the DBMS connection. The application-provided user ID and password are used in the DBMS context to access the DBMS machine.

When Vnode_usage is set to LOGIN, both connection and login VNODE information is used to access the DBMS machine. The application-provided User ID and Password are used in the DAS context, allowing access to private and global VNODEs on the DAS server.

The .NET Data Provider supports IPv6 addressing. IPv6 addresses should be enclosed in brackets [ ] because of the different address format--for example: [fe80::127:dff:fe7c:fecc].

If a hostname is associated with multiple IP addresses, the data provider sequentially tries to connect to each IP address in the AddressList returned by System.Net.Dns.GetHostEntry until it achieves a successful socket connection or until it reaches the end of the list. If the connection to the first address is down, the driver attempts a connection to the next entry in the AddressList. Although performance will suffer as each Exception from a failed connection is caught, this re-attempt allows a secondary IP (backup) for a connection to a server.