I am on a RHEL server with Oracle 19c. I issue the command 'rman' with no parameters. I am expecting to receive an RMAN> prompt at which point I can issue a connect command.
However RMAN immediately connects to whatever database I have specified by ORACLE_SID. Furthermore, if I unset ORACLE_SID and issue an 'rman' command with no parameters, I get an 'ORA_12162: TNS:net service name is incorrectly specified' error and no RMAN> prompt.
Why is this happening and how can I prevent rman from automatically attempting to connect to a database at startup?