Is purge participent cache necessary while using ad groups for license

I am using Windchill PDMLink Release 12.1 and Datecode with CPS 12.1.2.16 We are currently looking for possiblities to use AD groups for License profiles, but when we add/remove users from AD, users are not able to access windchill though we can see windchill License profile udner user information. Only after participant cache clear, user is able to login to widchill, is this behaviour correct or we are misisng something. is purge participent cache necessary while using ad groups for license?