A Start of Authority (SOA) Record tells the server to be authoritative for the zone. The SOA contains information about the zone, including the primary name server, the email of the domain administrator, the domain serial number and the number of seconds a secondary name server should wait before checking for updates; the number of seconds a secondary name server should wait before retrying a failed zone transfer; the maximum number of seconds that a secondary name server can use data before it must either be refreshed or expire; and a default number of seconds for the time to live (TTL) file on resource records.
See also:
Zone
Authoritative
Primary Field
Hostmaster field
Serial Number Field
Refresh Field
Retry Field
Expire Field
Minimum Field
Resource Record