I have received some questions on how does Dynamics AX 2012 decide what on-hand to select when reserving. Some thinks it is the inventory model (FIFO etc), but it is not. Some times it can seam like AX 2012 has it’s own will can selects randomly.
If the same item is located in many different buffer locations, there is a rule. It all comes down so sorting of inventory dimensions, that is specified in the InventoryDimensions group on the table InventDim.
So this means that the Inventsum is sorted on these inventory dimensions alphanumeric ascending. Meaning that items on location A001 will be reserved before A002 if available physical.
If you dig deep into the following method you find the code (InventSum::newQueryReservation()):
There are ISV solutions that addresses this, and that solves this in a very elegant way. But now you know where to look if you want to challenge reservation sequence in AX 2012 with a good old customization.
(There are FEFO reservation sequences in AX 2012 but this is not addressed here)