Can I fork child processes after SQLDriverConnect and use the connection handle in each one?

No.

The Easysoft ODBC-ODBC Bridge client connects to the ODBC-ODBC Bridge server during the SQLDriverConnect call. After SQLDriverConnect returns, a socket opens between the client and server. If you then fork children, they inherit the dbc and open socket. If the children use the dbc in further SQL function calls, multiple processes will send data down the same socket. This does not work. You need to make the SQLDriverConnect call in each child.