Question concerning new CUM PTF A for 8.7

Document ID : KB000121440
Last Modified Date : 24/12/2018
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Applying CUM PTF A for 2E 8.7 and the order of the YAPYMDLCHG command:
We are about to run some tests with the CUM PTF A for 2E 8.7.
As we have a customer who is planning an upgrade from 8.5 SP1 to 8.7, we will of course also made the CUM PTF A available to him.
We have the following question concerning the order of the YAPYMDLCHG command:
With 8.7 GA it is necessary to add special fix Y28700554 to the library list to remedy the problem that MSGIDs are being blanked out by the YAYSYSMDL comand.
We saw that the mentioned special fix is now included in the CUM PTF.
Could you please ask what Level 2 recommends concerning the order of YAPYMDLCHG ?
Can the customer add the CUM PTF A libs in the library list, and run the YAYPMDLCHG in order to avoid the special fix from 8.7 GA ?
Or is it saver to apply the YAPYMDLCHG command first with the GA 8.7 version (thus adding the special fix) and running the CUM PTF A steps later ?
In our tests we saw that either way worked for our small test models, i.e. the message ids are not blanked out.
But not knowing what additional steps the YAPYPTF command internally runs, we are asking which way is the better one for customers with huge models in order to avoid problems during the model upgrade. 
Add the CUM PTF A libraries to the upgrade library list and then run the YAPYMDLCHG command. This way they can avoid specifying the Test PTF provided earlier for the model upgrade and still ensure that the MSGIDs are not blanked out during YAPYMDLCHG processing. However, after the YAPYMDLCHG processing is completed, they will still have to use YAPYPTF to apply the CUM PTF A to the user model. Just including the CUM PTF A libraries in the library list does not mean they have been applied to the user model. They have to be explicitly applied by using the YAPYPTF processing.