When the Oracle client software has not been properly installed, you will get an exception when trying to connect:
[FireDAC][Phys][Ora]-1309. OCI is not properly installed on this machine (NOE1/INIT)
http://docs.embarcadero.com/products/rad_studio/firedac/frames.html?frmname=topic&frmfile=Connect_to_Oracle_Server.html
