Meaning of "Union Policy" in JSS MCX settings?

[robo]

Could someone explain or point me in the right direction for understanding what the "This setting is part of a Union Policy" checkbox and associated options are all about?

I am having no luck finding any documentation of this, or even discussion about it, on the web or within JAMF Nation, other than a few people's examples of settings they use that use this...

Puzzled...

Thanks,
Robin

[gregneagle]

You'll have better luck if you remember that this is JAMF's implementation of Apple's technology. Searching for "MCX union policy" returns several promising links:

https://developer.apple.com/library/mac/#documentation/MacOSXServer/Conceptual/Preference_Manifest_Files/Chapter_1/PM_Chapter1.html:
"Union policy keys provide a way to specify behavior when two or more preference keys come into play as the result of a single event. "

http://www.bresink.com/osx/300268194/Docs-en/pgs/ManifestViewer.html:
"A union policy is used by MCX to combine values of already present settings to produce a new setting when the management actions takes place. There can be one or more input settings whose names are listed as input keys, and one single output setting, merging the values either into an array or a dictionary."

[clifhirtle]

I had the same question a while back Robin, found similar articles to what Greg references, and assumed it just meant that you mashing together different managed preference settings. My guess is you're using this when you know that the setting you're looking to manage already exists and you'd rather try and merge the values than overwrite them. But that just my guess here and would defer to others for confirmation.

[robo]

Thanks! I don't know how I did not find those before, I guess I was getting tunnel vision and assuming this was a JAMF specific thing.

If I'm understanding the documents correctly, 1.) it is a way of specifying how user, group, computer, etc MCX should be merged when they are managing the same array or dictionary, and 2.) it only has an effect when the application has a Preference Manifest File containing a Union Policy key for that setting...

[gregneagle]

robo - that sounds about right.