If we try to delete a DNS virtual service that is configured under 'Administration -> System Settings', we get the following error: "<dns-vs-name >cannot be deleted! <dns-vs-name> is being referred to by SystemConfiguration object."
The DNS virtual service cannot be deleted if it is being configured inside the system settings.
To successfully delete the DNS virtual service, it first needs to be disassociated from the System settings.
You can do so by removing the virtual service from 'DNS services' under 'Administration -> System Settings'.
Screenshot of the DNS services location in the system settings: