How does the ATP/CTP function works


I want to know how the ATP function works. The information I found on web or in the books is either insufficient or confusing.


It looks at what you have in stock and what you don’t. Create an item with a lead time and switch on reservations, load a sales order you will get a date, then cancel the line, load some stock and load another and you will get a date - compare them. It is based upon what is available. CTP is in your title but not your question, so this only relates to ATP. What have you tried and why is it insufficient?

Thanks Adam.

I am trying to run a scenation where we have a kit item having 3-4 component items. I have created a BOM for the Kit. I have setup CTP for the Kit & ATP for the components. For a sales order of the kit, how should the date be calculated?


How have you set CTP for the parent and ATP for the components - please explain your setup to us to understand.

The Inventory is not maintained for the Kit. For a kit, all the components are assembled together & shipped. So the delivery date for the kit should be calculated on the basis of the components’ inventory & the purchase lead time.

That’s why I have setup CTP for the Kit & ATP for the components.

Tell me the field you have set on the item to achieve ATP for components and CTP for Kit.

On the default order settings form for the kit Item; I selected CTP as the delivery date control method.

Similarly I have setup ATP for the components.

Okay I believe in that instance it will look at the CTP value of the parent and see what it could possibly do based upon the resources, whilst using the ATP to look at the material of the components. So it depends what you are trying to achieve. If you set your resources to infinite then you are looking at the ATP of the components. I suggest you create a simple BOM with one line and have it set to infinite, then start playing with the capacity settings and the stock to impact on the CTP and ATP calculations.