Hi Sk,
I do not know how your idoc process is working - you need to provide more details on that.
But VA01 sounds like it is working correctly.
The First Date represents the "Requested Delivery Date". This should not change because the route changes. Lets take an example:
I create an order today with a requested delivery date (first date = 20th June). The system calculates the following:
Delivery date D 20.06.2013
Goods issue date 19.06.2013
Loading date 19.06.2013
Material avail.date 19.06.2013
Transportation Plan. Date 19.06.2013
^^My sample route has a transit time = 1.
If I change the route in the item, the system should not change the first date. But it should change the scheduling result. For example, if I change it to a route with a transit time = 10 days, scheduling will change to:
Delivery date D 20.06.2013
Goods issue date 05.06.2013
Loading date 05.06.2013
Material avail.date 05.06.2013
Transportation Plan. Date 05.06.2013
(if you do not allow dates in the past, then the system will create a new schedule line), In this example, dates in the past are allowed. The "First Date" should not be changed because the route has been changed - this is still the customer required date. The system calculates all the other scheduling dates based on the entered "First Date". It does not calculate the shipping dates on the basis of the route entered (the route is considered for the GI date) but the first date is the basis for the scheduling of the sales order.