Hi
There isn't any specific upgrade for byod services.
The upgrade process is the same and may have a downtime depending on your design. Take a look at this Cisco documentation:
http://www.cisco.com/c/en/us/td/docs/security/ise/2-2/upgrade_guide/b_ise_upgrade_guide_22/b_ise_upgrade_guide_22_chapter_01.html
While doing the upgrade, you need to ensure that no trusted certificate is expired otherwise your upgrade is gonna fail.
Except that, it's more than recommended to export your certificates. If something bad happens you'll be happy to get this backup and not losing everything.
Thanks
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Thanks
Francesco
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