BMS (Building Management System)

A building management system (BMS), also called a building automation system, is the control layer that monitors and operates a data center's mechanical and electrical plant — chillers, CRAC/CRAH units, generators, switchgear, and fire suppression — typically over protocols such as BACnet or Modbus. It is distinct from DCIM, which overlays IT-asset and capacity data on top of the facility; in practice the two integrate, with DCIM pulling power and thermal telemetry from the BMS to compute metrics like PUE and drive capacity planning. The BMS handles real-time setpoint control and alarm response, for example staging chillers or switching to free cooling as outside-air temperature drops, while DCIM focuses on asset inventory, billing, and longer-range forecasting for IT and facilities teams. Major BMS vendors active in colocation facilities include Siemens, Johnson Controls, Honeywell, and Schneider Electric, often the same suppliers behind widely used DCIM platforms.