Hi
explanations of Balajee a very helpful. But I would like to add some info:
You have material X assigned to specification X, and you have material Y assigned to specification Y.
Both will get data in property tree. Based on the data both will get a dangerous goods master. Now you perform a "physical" mix. Therefore you need a new material Z and a new specification Z. Then once again data is maintained and DG classification need to be done and therefore Z will get its own dangerous goods master data.
But it seems to be that during filling of dangerous goods master of material Z an error message come up. Here I believe the approach/hint of Sunil might help.
But from business point of view (maintenance etc.) it seems to be that you have prepared set up correct.
PS: please read cross the DG filling part of SAP online help; there are a number of subprocesses involved which I did not mentioned here assuming that you are not using these in your scenario; but this assumption might be wrong; I am sorry. In contrast to SDS distribution no OSS consulting note is available explaining the DG part of SAP EHS.
C.B.