Here's what a friend said:
The guys ordering at the Hummer dealers are working with the GM Vechical Order Managemernt System VOM they call it VOMs (sometimes "vomit"
You need to speak to that guy because he will know what is going on.
On Thursday dealers recieve their allocations. They find out what is available to them of all makes and models that they carry. They find out what they "earned" in allocations. Larger dealers will have earned greater allocations.
During the week they can also recieve "Memos" from GM that discuss constraints. These Memos might tell them for example that sunroofs might not be availalbe for 4 months (example) and to go ahead and only place orders without them. IN this case the sunroof would be considered to be on National constraint.
When they look at their allocations on Thursday for how many H3's they have (if they have allocations) they can try to create an order. When they are using the VOM they might find that they only have an allocation for 2 hummer H3 without sunroofs and 2 hummer H3 with sunroofs. So the sunroofs might be on constraint but the constraint is not a National constraint. If there are no sunroofs available to any dealers then they are said to be on National constraint and no dealers will be able to place an order for a H3 with a sunroof.
If the dealer working with the VOM has two H3s without sunroof and 2 H3s with sunroof the dealer might choose "which" customers that want sunroofs will be associated with that allocation. So if you have a lower priority on the dealers list you will have to wait until they recieve their next allocation of H3s with sunroofs because you have been bumped.
Ask the dealer if the sunroofs are on National constraint (no dealers can place an order for a sunroof H3). If it is not a National constraint then it is just an allocation issue.
The dealer recieves allocation information on all GM vechicals on Thursday and knows if the order was accepted on Tuesday.