A data management process determines, from user-implemented provisional reservations (400) for data processing resources, a projected total capacity requirement for each said data processing resource, by maintaining a record (9, 90, 91) recording previous such reservations made by each user and comparing each reservations with records (87, 88, 89) of the actual resources used, to provide an estimate of resources required to meet the projected capacity requirement, and to provide data for a demand management processor (2), which control associated configurable data processing equipment (1) to provide the resources required to meet the estimated capacity required. The process takes account of over- and under-ordering of capacity by comparing each reservation (400) with the use actually made (600), and includes a record (10) of ad-hoc (unreserved) usage.