If you come across a situation that you want to use RMAN to restore but there is a backup without using RMAN.
When you try to restore using RMAN you will receive the error message as below
RMAN-06023: no backup or copy of datafile xx found to restore
When you query catalog you will get below message as no backups in repository.
RMAN> LIST BACKUP OF DATABASE;
Specification does not match any backup in the repository
If you want to use the backups taken using HOT backup mode or copy, you must register all data files, archive logs into RMAN catalog.
Use below command to register.
RMAN> catalog start with '/ora-backup/ORCL/arch-bkp/' noprompt;
RMAN> catalog start with '/ora-backup/ORCL/data-bkp/' noprompt;
If your archive logs and data files are in same location then you need to run only once.
Once all backup copies are registered in RAM you can follow below link to restore
Satishbabu Gunukula, Oracle ACE