Any Oracle user with SYSDBA role can run RMAN backup, so we suggest creating a dedicated user (rman) for that matter. Make sure that the number of entries in the password file leaves you room for adding one more user. If not, then use one of the existing sysdba users. For security reasons, it is slightly better to use a user with SYSDBA role who lacks “CREATE SESSION” privilege, so it cannot be used as a regular user.
conn sys AS SYSDBA CREATE USER rman IDENTIFIED BY password; GRANT SYSDBA TO rman;
To find existing users with SYSDBA role, see my recent post.
To find the maximum number of entries in the password file, use the formula:
Take the size of the password file (in bytes), subtract 1024 (header size) and divide by 128 (number of bytes per 1 entry)