If a problem prevents the system from booting successfully or some other severe problem occurs, you will need to boot from a network install server or from a Solaris installation CD, import the root pool, mount the ZFS BE, and attempt to resolve the issue.
Boot from an installation CD or from the network.
SPARC:
ok boot cdrom -s ok boot net -s  | 
If you don't use the -s option, you will need to exit the installation program.
x86: Select the network boot or boot from local CD option.
Import the root pool and specify an alternate mount point. For example:
# zpool import -R /a rpool  | 
Mount the ZFS BE. For example:
# zfs mount rpool/ROOT/zfsBE  | 
Access the ZFS BE contents from the /a directory.
# cd /a  | 
Reboot the system.
# init 6  |