The primary difference between Capable-to-Promise (CTP) and Available-to-Promise (ATP): ATP considers the material availability for the requested Product, but assumes infinite capacity on the production side, while CTP aims to extend ATP by taking into consideration lead times, routings and alternative routings, and finite capacity, giving a more accurate guess as to when a customer might expect their order to be completed.
ATP in APS
ATP is managed in APS as a field within the Inventory Plan labelled “ATP Qty”. This is the quantity of the specified material that is currently available to be “promised” to a customer without affecting existing commitments. This quantity is calculated as the minimum projected inventory level from the current date out into the future.
CTP in APS
CTP is closely related in concept to the idea of What-If Scenarios and can be found in the same tab on the navigation ribbon of APS. As a separate dialog box, the key data points that will be required in order to submit a CTP request would be the Item, how much of that item is required, when it will be required by, and what routing (if there are several alternatives to choose from) to use to create the Item. The Warehouse selections will determine where the individual materials can come from, if they can come from different sources or must all come from the same Warehouse.
Once the CTP has been submitted, APS will project a Start and Finish time as well as whether or not it expects the Job to be late, early, as determined by the current Optimization Rules. If the Job is projected to be late, APS will determine which constraints are bottlenecking the process.
APS will also allow the CTP to reserve Capacity and Materials until a user-defined date, allowing the customer some time to determine whether or not to go through with the order.