Installing when booting a system backup fails
If a backup tape fails to boot, you can still install by using a mksysb image stored on the tape.
Boot the machine from the product media (Volume 1 if there is more than one volume), then install the backup from Maintenance mode. For instructions on booting, refer to Installing the Base Operating System. Follow the instructions to the point when the Welcome to the Base Operating System Installation and Maintenance screen displays.