To update packages on an existing, inactive boot environment, mount that environment first, in order to gain access to it, Then, you can update packages on it.
The beadm mount command mounts a specified boot environment at a specified mount point. If the mount point already exists, it must be empty. If the directory for the mount point does not exist, the beadm command creates the directory, then mounts the boot environment on that directory. Although the boot environment is mounted, it remains inactive.
If the specified boot environment is already mounted, the beadm mount command fails and does not remount the boot environment at the newly specified location.