Question about ATP check using BAPI_MATERIAL_AVAILABILITY

Question

In the user exit for delivery creation, I'm doing an additional ATP check using the BAPI_MATERIAL_AVAILABILITY based on this topic's recommendation:  FM to check available stock
However, my code checks both of these in determining that ATP quantity is available:
1) DIALOGFLAG not equal 'X'
2) Value of COM-QTY for the requested date (in return table WMDVEX) is greater or equal to zero.
The second check was something I derived, and appears to work 100% of the time for all our cases. 
The DIALOGFLAG check is an enigma.  I can't recall which post or OSS I saw this in, but it stated that DIALOGFLAG = 'X' indicates no ATP quantity available?  However, we've had a couple of orders in the last week, where the ATP quantity was greater than zero at the time the delivery was posted, but BAPI_MATERIAL_AVAILABILITY returns an 'X'.
So... my question is what does the "X" really mean in terms of ATP?  Does it indicate (a) that the ATP quantity is zero at the end of timeframe (which it was), or (b) something else I don't know about?

Answer 1

Hallo Brad Bohn,
thank you for your suggestion.
Iu2019m using an own rule (as copy of rule A), the own rule donu2019t use purchase orders.
In CO09 I have the following ATP Quanties:
09.09.2009     BStand          1,775     0     259
09.09.2009     LgBest     0001     785     0     459
09.09.2009     LgBest     0002     989     0     452
09.09.2009     LgBest     0003     22     0     20
The function module provides only 259 for each storage location.
There is another function module AVAILABILITY_CHECK. Can this function module also be used to determine ATP quantity?
Thank you & best regards,
Kurt.