Okay I'm turing to the guru's for this one. After much research and hair pulling. I have been trying to find a way to locate Oracle instances within our enterprise, where the tnsnames information as been lost. Example the rman catalog is used for backups, but after looking through every document and logging on to most if the servers. I can not find the rman DB.

The Question: is there a way to find Oracle instances that you do not have a refrence for?

OPP

There is NOT a 100% all the time reliable method.
Locating & dissecting listener.ora will likely prove better than some/many/most methods.

HTH & YMMV