You might need to boot the system to resolve a corrupt bootloader problem, a root password problem, or a bad shell. For the recovery procedures for each of these cases, see Shutting Down and Booting a System for Recovery Purposes in Booting and Shutting Down Oracle Solaris 11.3 Systems.
If you need to replace a disk in root pool, see Replacing Disks in a ZFS Root Pool. If you need to perform complete system (bare metal) recovery, see Using Unified Archives for System Recovery and Cloning in Oracle Solaris 11.3.