http://SERVERNAME
Enter following information.
Oracle APPS User Name and Password, Host Name, SID
Click on "Enter AOL/J Setup Test" in the AOL/J Diagnostic Tests page
Click on "Locate DBC File"
Typically it is at $INST_TOP/appl/fnd/12.0.0/secure/.dbc in application server.
Pre R12
$FND_TOP/secure/.dbc file.