Start Of Authority (SOA)
The Start Of Authority (SOA) record is always first in Domain Name System (DNS) zone file it shows the entity responsible from this point in the hierarchy downward.
The information in zone files can be viewed using the Domain Name Service Manager utility. In the example The Name Server (NS) identifies the computer located at dnsserver.themob.co.uk as the DNS server. The SOA record shows that the DNS server is also responsible for the themob.co.uk domain. The A record provides the IP address of dnsserver.themob.co.uk.