Is GTS instanced between generations?

So when i search for Arceus on my pokemon Sun i get no results. While if i search for Arceus on Omega Ruby i get a handful of results that are fast moving (new trades come up and go down for it frequently) this is the same with a handful of other pokemon, seemingly the GTS on either game is different? how many different GTS systems exist? i've noticed my edit: *old* games have discontinued online services. Does Black 2 have its own GTS? or is it tied to Omega Ruby GTS?

It's basically a generational thing. You can't trade on the GTS between generations, so what's available on XY/ORAS isn't available on Gen 7 and vice versa. And then both of these are separate from the Gen 4 and 5 GTSs, which don't function/have activity now anyway.

oh cheers! damn i gotta read stickys, didn't notice the difference between pokemon general and pokemon gaming