After rman target / I am connected to my local database, however I would like to connect to database to which I have credentials - ip, port, username, password (in general to which I can connect via SQLDeveloper). Is it possible through RMAN?
It isn't shown in the documentation, but you can use 'easy connect' syntax:
rman target user@hostname:port/servicename
or if you don't want to be prompted for the password (less secure!):
rman target user/password@hostname:port/servicename