This works for OBIS but for admintool does not work
Have you got a tnsnames.ora file in the right place?
https://support.oracle.com/knowledge/Enterprise%20Performance%20Management%20and%20Business%20Intelligence/2068474_1.html
Also it depends on where you Admin Tool is running? Are you using a Windows server and the Admin Tool is in the same place as the OBIEE installation? Then the Admin Tool and OBIEE (the server) can use the same connectivity innformation.
What you say point to you running the Admin Tool on a different machine - like a desktop - though. That means that THAT machine, your desktop, must have its own connectivity to the Oracle databases with a valid Oracle client installation on the machine. Then the Admin Tool will use that connectivity. Your local Admin Tool can't "magically" use the connectivity of the OBIEE server.
No, I am running Admintool from the same OBIEE Server
