Changing the cookieName will cause all your users to reset, this means everyone will get a new
domain_userid and all their session information will reset too (
To avoid this you’d need to write some custom logic to migrate the cookies over for your users (i.e. read them and rewrite them before the tracker initialises). There’s currently nothing in the tracker that can do this for you.
One other option you have is if you are tracking on a first party domain (i.e. the collector url is on the same parent domain as the website), then the
network_userid should remain stable for a user, so you could potentially stitch the updating
domain_userid values to their old ones, although session information will still reset.
Beyond the migration issues, theres no other issues that you should face when changing the cookieName.