Aging and Scavenging Parameters
The Windows 2000 DNS server uses the timestamp that it gives each record, along with parameters that you configure, to determine when to scavenge records.
Table 6.9 lists the zone parameters that affect when records are scavenged. You configure these properties on the zone.
Table 6.9 Aging and Scavenging Parameters for Zones
Zone Parameter |
Description |
Configuration Tool |
Notes |
|---|---|---|---|
No-refresh interval |
Time during which the server does not accept refreshes for the record. (The server still accepts updates.) |
DNS console and Dnscmd.exe |
When an Active Directory–integrated zone is created, this parameter is set to the DNS server parameter Default no-refreshinterval . |
Refresh interval |
The refresh interval comes after the no-refresh interval. At the beginning of the refresh interval, the server begins accepting refreshes. After the refresh interval expires, the DNS server can scavenge records that have not been refreshed during or after the refresh interval. |
DNS console and Dnscmd.exe |
When an Active Directory–integrated zone is created, this parameter is set to the DNS server parameter Default refresh interval . |
Enable Scavenging |
This flag indicates whether aging and scavenging is enabled for the records in the zone. |
DNS console and Dnscmd.exe |
When an Active Directory–integrated zone is created, this parameter is set to the DNS server parameter Default enable scavenging . |
ScavengingServers |
This parameter determines which servers can scavenge records in this zone. |
Only Dnscmd.exe |
This parameter is replicated by Active Directory. |
Start scavenging |
This parameter determines when a server can start scavenging of this zone. |
Not configurable |
This parameter is not replicated by Active Directory. |
Table 6.10 lists the server parameters that affect when records are scavenged. You set these parameters on the server.
Table 6.10 Aging and Scavenging Parameters for Servers
Server Parameter |
Description |
Configuration Tool |
Notes |
|---|---|---|---|
Default no-refresh interval |
This value specifies the no-refresh interval that is used by default for the Active Directory–integrated zone. |
DNS console (shown as No-refresh interval ) and Dnscmd.exe |
By default, this is 7 days. |
Default refresh interval |
This value specifies the refresh interval that is used by default for the Active Directory–integrated zone. |
DNS console (shown as Refresh interval ) and Dnscmd.exe |
By default, this is 7 days. |
Default Enable Scavenging |
This value specifies the Enable Scavenging parameter that is used by default for the Active Directory–integrated zone. |
DNS console (shown as Enable scavenging )and Dnscmd.exe |
By default, scavenging is disabled. |
Enable scavenging |
This flag specifies whether the DNS server can perform scavenging of stale records. If scavenging is enabled on a server, it automatically repeats scavenging as often as specified in the Scavenging Period parameter. |
DNS console, Advanced View (shown as Enable automatic scavenging of stale records ) and Dnscmd.exe |
By default, scavenging is disabled. |
Scavenging Period |
This period specifies how often a DNS server enabled for scavenging can remove stale records. |
DNS console, Advanced View (shown as Scavenging Period ) and Dnscmd.exe |
By default, this is 7 days. |
Record Life Span
You can also invoke the Active Directory Installation wizard by executing an answer file that contains all of the settings that you need to configure. An answer file is a file that a wizard uses to provide answers to questions. For more information about the answer file for the Active Directory Installation wizard, see "Active Directory Data Storage" in the Microsoft ® Windows ® 2000 Server Resource Kit Distributed Systems Guide .
Figure 6.22 shows the life span of a scavengeable record.
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Figure 6.22 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 timestamp is written.
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Caution
Because of the addition of the timestamp, a standard primary zone file for which scavenging is enabled is has a slightly different file format than a standard DNS zone. This does not cause any problems with standard zone transfer. However, you cannot copy a standard zone file for which scavenging is enabled to a non-Windows 2000 DNS server.
The value of the timestamp is the time the record was created or the record was last refreshed. By default, if the record is not dynamically updated, the timestamp equals zero, and the record is not scavengeable. Also, the timestamp is never changed if it contains a zero value. If the record belongs to an Active Directory–integrated zone, then every time the timestamp is refreshed, the record is replicated to the 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.
After the record is refreshed, it cannot be refreshed again for the interval 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 modification to a record, the request is considered an update. If the request requires no 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, and the server continues to accept refreshes for the life span of the record. 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 the record at that time. The time at which records are scavenged depends on several server parameters.