User blog comment:Mich, Michele & Kuhla/Guide: UBB and the OD gauge/@comment-124.106.157.63-20150827080222

OD is shared by all units in your squad, and thus can be filled faster if you have a full squad with UBB unlocked though you can only use 1 UBB per OD Maxed.. It is suggested to OD the unit you want to use it's UBB before letting the other units to attack..