Restoring Without a Backup History 
Prerequisites
The
database instance is in
operational state ADMIN.
The
backup history contains errors or is no longer complete.
Procedure
backup medium is to be read back in. The system default is the current time. If you do not change the time proposed by the system, the backups are restored completely and with all the changes they contain.
external backup IDs.

You can if you wish stop the restore process and resume it later on (see