MPC execution systems (back end): the outputs from material and capacity plans in the engine are sets of instructions to suppliers, manufacturing and distribution. These schedules are in the form of purchase orders, works orders (or schedules for MTS) and shipping orders – hence the familiar ‘source–make–deliver’ processes at the bottom of Figure 6.1. The basic format is ‘how many’ and ‘when’ for each part number for each planning process for the relevant planning period (for example the next two weeks, or the next four weeks). Achievement against schedule has to be monitored by minute, by hour or by day. Failures to meet schedule – as a result of for example breakdowns or quality problems – require that remedial action is taken, such as overtime working or outsourcing. An example here is the Nokia supply problem described in Case study 1.4.