If an attempt to connect to a primary server fails, dbopen can attempt to connect to a fallback server. You must call the DBSETLFALLBACK function to indicate that a fallback server can be used. The call to the DBSETLFALLBACK function must occur before the call to the dbopen function.
Each call to the DBSETLFALLBACK function from a machine running Windows NT or Windows 95 updates the fallback information in the local registry from the SQL Server registry. Fallback information is stored in the WIN.INI file on machines running 16-bit Windows. The dbopen function retrieves the fallback information from the local registry or from the WIN.INI file.
When dbopen attempts to connect to a fallback server, DB-Library generates warning message 10110 (SQLECONNFB):
Unable to connect: DB Server is unavailable or does not exist -- will attempt a fallback connection.