AFAIK, and my Viya knowledge is pretty basic, Viya uses external OS identities only. There is no concept of SAS internal accounts as in SAS 9.x where these are defined only in SAS metadata and nowhere else. There is no metadata repository in SAS VIya, so access is controlled by OS user and their permissions that are synchronised using an interface to LDAP. So the OS user accounts are created in Active Directory or similar tool and then synchronised with Viya.