If you run RMAN with a respository, then oracle will store that information in tables in this database.
Data will be kept and grow (just like all tables) and then rman management will be needed to
remove obsolete records.
When you do not use a recovery catalog, the control file is the sole source of information about RMAN backups. As you make backups, Oracle records these backups in the control file. To prevent the control file from growing without bound to hold RMAN repository data, records can be re-used if they are older than a threshhold you specify.
The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter determines the minimum age in days of a record before it can be overwritten:
CONTROL_FILE_RECORD_KEEP_TIME = integer
For example, if the parameter value is 14, then any record aged 14 days and older is a candidate for reuse. Information in an overwritten record is lost. The oldest record available for re-use will be used first.
When Oracle needs to add new RMAN repository records to the control file, but no record is older than the threshhold, Oracle attempts to expand the size of the control file. If the underlying operating system prevents the expansion of the control file (due to a disk full condition, for instance), Oracle overwrites the oldest record in the control file and logs this action in the alert log.
The default value of CONTROL_FILE_RECORD_KEEP_TIME is 7 days. If you are not using a recovery catalog, then set the CONTROL_FILE_RECORD_KEEP_TIME value to slightly longer than the oldest file that you need to keep. For example, if you back up the database once a week, then you need to keep every backup at least a week. Set CONTROL_FILE_RECORD_KEEP_TIME to a value such as 10 or 14.