A living operational record of a building - how its systems are meant to be run, key contacts, and performance targets - kept updated throughout its life, not just handed over once. Unlike a static O&M Manual delivered once at handover, a log book is meant to be a living document that gets updated as equipment is replaced or operating strategies change - a Soft Landings requirement that treats the building's documentation as something that ages with the building itself, not a one-time deliverable.