You can change an inactive boot environment into an active boot environment, which means that the named boot environment will be used when the system is next rebooted. Only one boot environment can be active at a time. The newly activated boot environment becomes the default environment upon reboot.
Use the beadm activate command as follows to activate an existing, inactive boot environment:
# beadm activate BeName
beadm activate sets the specified boot environment as the default in the menu.lst file.