This document: a) describes the general principles for data centres upon which the requirements of the EN 50600 series are based; b) defines the common aspects of data centres including terminology, parameters and reference models (functional elements and their accommodation) addressing both the size and complexity of their intended purpose; c) describes general aspects of the facilities and infrastructures required to support data centres; d) specifies a classification system, based upon the key criteria of “availability”, “security” and “energyefficiency” over the planned lifetime of the data centre, for the provision of effective facilities and infrastructure; e) details the issues to be addressed in a business risk and operating cost analysis enabling application of the classification of the data centre; f) provides reference to operation and management of data centres; g) introduces the concepts of Key Performance Indicators (KPIs) for resource management of data centre facilities and infrastructures.