A Start of Authority record (abbreviated as SOA record) is a type of resource record in the Domain Name System (DNS) containing administrative information about the zone, especially regarding zone transfers. The SOA record format is specified in RFC 1035.
Normally DNS name servers are set up in clusters. The database within each cluster is synchronized through zone transfers. The SOA record for a zone contains data to control the zone transfer. This is the serial number and different timespans.
It also contains the email address of the responsible person for this zone, as well as the name of the primary master name server. Usually the SOA record is located at the top of the zone. A zone without a SOA record does not conform to the standard required by RFC 1035.