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Record Life Span
The Figure below shows the life span of a scavengeable record.
When a record is created or refreshed on an Active Directory–integrated zone or on
a standard primary zone for which scavenging is enabled, a record’s timestamp is
written.
Because of the addition of the timestamp, a standard primary zone file for which
scavenging is enabled has a format slightly different from a standard DNS zone file.
This does not cause any problems with zone transfer. However, you cannot copy a
standard zone file for which scavenging is enabled to a non-Windows 2000-based
DNS server.
The value of the timestamp is the time when the record was created or the record
was last refreshed. If the record belongs to an Active Directory–integrated zone,
then every time the timestamp is refreshed, the record is replicated to other domain
controllers in the domain.
By default, the timestamps of records that are created by any method other than
dynamic update are set to zero. A zero value indicates that the timestamp must not
be refreshed and the record must not be scavenged. An Administrator can manually
enable aging of such records.
After the record is refreshed, it cannot be refreshed again for the period specified by
the no-refresh interval. The no-refresh interval, a zone parameter, prevents
unnecessary Active Directory replication traffic.
However, the record can still be updated during the no-refresh interval. If a dynamic
update request requires record modification, it is considered an update. If it does
not require record modifications, it is considered a refresh. Therefore, prerequisite-
only updates—updates that include a list of prerequisites but no zone changes—are
also considered refreshes.
The no-refresh interval is followed by the refresh interval. After the expiration of the
no-refresh interval, the server begins to accept refreshes. The record can be
refreshed as long as the current time is greater than the value of the timestamp plus
the no-refresh interval. When the server accepts a refresh or an update, the value
of the timestamp changes to the current time.
Next, after the expiration of the refresh interval, the server can scavenge the record
if it has not been refreshed. The record can be scavenged if the current time is
greater than the value of the timestamp plus the value of the no-refresh interval plus
the value of the refresh interval. However, the server does not necessarily scavenge
Windows 2000 White Paper 26