ATP and CTP Become Distinguishing Network Features

The application of ATP was an outcome of the understanding of the structure used in the processing behind MRP. It is the result of linking bills of material, routing, and inventory with demand in the unified 

The each request works best when there is agreement on what is available, as in the case of airline seats. Each passenger requires one seat. In the application of CTP, the problem of the unit of measure of each is a world filled with features and options, which implies there are many different interpretations between the potential requested each and what is modeled or structured by the producer as an available each. Under these conditions, it is exponentially more complicated —not only for the computer, but for the humans trying to model the amount of discretion in the system. When the product has any degree of variability in configuration and process, the result is poor capacity assumptions and lengthy system calculations from which a valid promise is difficult to make. 

CTP is based on capacity, or a model of the capability of the system to perform work. Capacity is a function of structure, BOMs, routings. 

ATP is again a bit more reliable as it is based on inventory, which is a function of the schedule or commitment to production. To handle the discretion applied to most demand, ATP relies foremost on what the system says is in inventory or stock buffers within the limits of the master schedule and not the flexible capacity of CTP. The problems with ATP are associated with the commitments or process difficulties. Externally, this implies that there is a potential problem with understanding the commitment of the buyer and matching it with the commitment to produce. The greater the uncertainty between the two factors, the more inventory or production is required for the producer. Internally, the ability of a company to promise from a schedule is quantified in classical measures inventory, bills of material, routing and master schedule accuracy. Again, it is inventory that is required to compensate for the lack of ability in these matters in order to keep promises. To measure the level of commitment or the ability the firm has for keeping its scheduled promises, you need only to look at the quality of its processes from which those promises are made. 

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