Similar to 4D Open connections, an application connecting via ODBC to 4D Server will consume a 4D Client license. Thus, if the 4D Server application serves a mixture of both 4D Clients and ODBC clients, there must be enough 4D Client licenses to accommodate the connections. Not having enough licenses will result in a 4D Client or ODBC client being denied access to the 4D server.

Furthermore, a single ODBC client may initiate 6 concurrent ODBC connections which will use one 4D Client license. On the 7th ODBC connection, another 4D Client license will be used if available. Please note that this applies for a single ODBC client application. If more than one ODBC client connects, each will consume a 4D Client license.

Related Resources:

Exploring ODBC connections with 4D:
https://kb.4d.com/assetid=4599

Tips on using the ODBC Driver for 4D Server:
https://kb.4d.com/assetid=4742

Creating databases that will be queried through the 4D Server ODBC driver:
https://kb.4d.com/assetid=9760

Multiple 4D Open for 4D Connections and 4D Server licensing:
https://kb.4d.com/assetid=9281