I installed Oracle Database Enterprise Edition 11g(220.127.116.11) in my machine. And I installed ArcMap Desktop 10.3.1 on another machine. Whenever I am trying to create a direct connection of Oracle DB from ArcMap without ArcSDE installation, I am getting the following error like "Failed to connect to the specified server. Do you want to continue? Bad login user". Even I have enabled the port in Oracle DB machine. I was giving the oracle server is the DB IPAddress, Instance Name is "orcl" and port is 1521.
Do I need to install Oracle Client software where the Oracle DB is existing and, if not, where I am lacking in this concept?