I am in the process of designing a UDI OSD deployment. The client has multiple sites each with their own set of non-core applications which has pushed the number of apps on the "Install Applications" page way past 256. I'm finding that if I add > 255 applications, I get an XML validation error when saving:
"Invalid XML File Warning : The identity constraint 'UniqueAppIds' validation has failed. Either a key is missing or the existing key has an empty node."
Unfortunately, it won't let me save the changes or view the xml it thinks it wants to generate.
As a test I manually edited the .xml.app file and added a new application as id=256. the UDI designer threw the same error when the "Install Applications" page is attempted to be loaded.
I have not found any references to there being a 255 limit to the number of applications on technet, or any other technical resources but if that is indeed a confirmed limitation, it would be good to know.
To recreate, simply edit any .xml.app file for a UDI and change one of the id="xxx" to id="256". It will cause an xml validation error to pop-up when loaded and you doubleclick on "Install Applications".
I have as yet to try changing the ID to 256 and then running an OSD to see if it still functions. It may just be an issue with the UDI Designer that comes with MDT 2012. If there's a patch or other workaround outside of splitting the pages, it would be good to know.
Just verifying if you are running into this issue for app model applications or package programs? If these are applications could you describe the scenario you mention for using multiple sites and their applications? I was wondering if the applications for every site were added to the same config? Do they have the same names on every site? Can you use multiple config files?
As you can only have 99 apps per base variable for app model apps I am not sure how many apps beyond that were tested being added to the page.