Question of apache configuration

Hi,

if I want my LAMP stack to answer requests to http://www.mydomain.com as well as for http://mydomain.com is this a question of how to configure the apache or also a question of DNS settings at my provider?
I assume the latter since www.mydomain.com might point to any other server then just mydomain.com. But which kind of DNS record to I need to apply there? I tried a CNAME record with “@” as host but that did not make the job.

Any idea?

Best regards,
Olaf