You can start using RMAN to back up and recover your databases with very little fanfare. When you install the Oracle server software, you'll automatically install RMAN as well. You only absolutely need two things to start using RMAN: the database you want to back up (referred to as the target database) and the RMAN client, which is the interface you use to interact with the RMAN server processes that perform the actual backup and recovery tasks.
When you use RMAN to back up and recover your database files and objects, you use the RMAN client to interact with the database. The RMAN client interprets the RMAN commands you issue and starts up the necessary server sessions to process those commands. The term RMAN repository