Below procedure explains you about ‘ booting from an alternate boot disk’

i)              ok printenv use-nvramrc?

If use-nvramrc? is set to true, this allows the use of alternate boot disks.

If use-nvramrc? is set to false, the system fails to boot from the devalias

and displays an error message such as the following:

Rebooting with command:

ok> boot vx-mirdisk

Boot device: /pci@1f,4000/scsi@3/disk@0,0 File and args:vxmirdisk

boot: cannot open vx-mirdisk

Enter filename [vx-mirdisk]:

ii)             ok setenv use-nvramrc? True

or

# eeprom use-nvramrc?=true

iii)            ok nvramrc=devalias vx-altboot_disk

or

# eeprom nvramrc=devalias vx-altboot_disk

iv)            ok devalias

Suitable mirror of the root disk are listed with names of the form VX-DISKNAME

v)            ok boot vx-altboot_disk