When providing ODBC or SQL access to your 4D Server, the 4D SQL Expansion license can be a lifesaver. This is because without the 4D SQL Expansion, each ODBC or SQL connection will consume a 4D Client License. This is particularly bad in the case of a malfunctioning ODBC/SQL Client that never logs out; in that situation you may find the exhaustion of licenses happens quicker then expected.

Depending on the number of client logging in, and the number of ODBC/SQL connections that you may get - compared to the number of client licenses you have - you may find yourself short of client access licenses. When this happens your end users may start to get licenses errors when trying to login.

The fix for this is to either purchase more Client licenses or to purchase the 4D SQL Expansion license.