Check the release notes for 8.11.2 for the upgrade procedure and eventually prerequisites. There are some mentions around memory, but it seems you can do a direct upgrade. Then first upgrade your MM/Mobility Conductors; when those are on 8.11.2, then upgrade your MC/Controllers.
------------------------------
Herman Robers
------------------------
If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
------------------------------