Which type of DNS zone is a read-only copy of the primary DNS zone?

A secondary DNS zone holds an exact read-only copy of the zone data from the designated primary DNS server, received via a zone transfer process (AXFR or IXFR). Administrators cannot modify records directly on a secondary zone - all changes must be made on the primary zone and then replicated, providing redundancy and load distribution while preserving a single authoritative write source.

The primary DNS zone is the authoritative, read-write source of zone records and is not a copy of anything.

A stub DNS zone contains only the SOA record, NS records, and supporting glue A records for the zone's name servers - it is not a full copy of the zone data.

SOA (Start of Authority) is a resource record type that exists inside a zone, not a category of DNS zone.