TIdDNSResolver.XFRType

Indicates the Zone transfer mechanism to use for resolving zone transfers queries.

XFRType is a TXFRTypes property that indicates the Zone transfer mechanism to use when QueryType contains the value qtAXFR and the Resolve method is called.

Value	Meaning
xtAXFR	Automatic zone transfer (AXFR) is used and transfers the entire zone file.
xtIXFR	Incremental zone transfer (IXFR) is used and transfers only the changed portion(s) of a zone.

Set XFRType when TIdDNSResolver is used to get zone information from a primary DNS server in order to repopulate values for a secondary DNS server.

When XFRType contains the value xtIXFR, you must provide the SOA serial number for the outdated copy of the zone information prior to calling Resolve.

Todo

How to pass the SOA serial number?

When updated zone information has been received, it should be saved in stable local storage before the contents of the zone information are used on the client.