A typical SOA record in BIND format looks like this:

example.com    IN    SOA    ns1.example.com. sysadmin.example.com.  (
                            2010121601    ; Serial (YYYYMMDD##)
                            3600          ; Refresh
                            900           ; Retry
                            1209600       ; Expire
                            3600 )        ; Minimum

The SOA record is defined in RFC 1035, and contains the following components:

MNAME           The <domain-name> of the name server that was the
                original or primary source of data for this zone.

RNAME           A <domain-name> which specifies the mailbox of the
                person responsible for this zone.  
                (By convention the @ sign is replaced with a period)

SERIAL          The unsigned 32 bit version number of the original copy
                of the zone.  Zone transfers preserve this value.  This
                value wraps and should be compared using sequence space
                (A common convention is YYYYMMDD## - where ## is a
                 serial number for the change within the given day)

REFRESH         A 32 bit time interval before the zone should be

RETRY           A 32 bit time interval that should elapse before a
                failed refresh should be retried.

EXPIRE          A 32 bit time value that specifies the upper limit on
                the time interval that can elapse before the zone is no
                longer authoritative.

MINIMUM         The unsigned 32 bit minimum TTL field that should be
                exported with any RR from this zone.
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