In disaster recovery when you have lost all database files, you will need to use your DBID. DBID should be recorded along with other basic information.
There are two places where you can find it without opening your database.
- DBID is the part of filename of control file auto-backup. Locate file
- Any RMAN saved session. DBID is displayed by the RMAN client when it starts up and connects to your database
RMAN> connected TO target DATABASE: RDBMS (DBID=774627068)