When I create an Oracle ADF BC project using Jdeveloper with 1 Application Module, it automatically establishes 3 connections to the databases. Is this correct behaviour? Why is it doing this? What's the minimum amount of connections that can be established?
That is correct when you create any ADF Business component it will create default DS with max connection pool size as 15 so it purely depends how many user will invoke that component based on it you can modify them.
for more details please go through following doc link.