Zone Boot environments that do not have any global zone BE associated with them - called orphan ZBE - are generally a byproduct of zone migrating from one host to another. Managing them is a tough 'nut to crack' as it requires mucky manual steps to get rid of them/retain them during migration or otherwise. Solaris 11.3 introduces changes to zoneadm(1M) and beadm(1M) to manage them better.
To find out more about these enhancements, click here
To find out more about these enhancements, click here