Aging and Scavenging Facts
Dynamic updating can cause your zones to become overloaded with unnecessary resource records. If a computer disconnects improperly from the network (as is often the case when you allow mobile users and computers on your network), the host (A) resource record it registered may not be removed. It is for reasons such as this that DNS records have a Time to Live (TTL) value. When a record exceeds its TTL, it becomes stale. Large numbers of stale records can cause long zone transfers and name resolution problems. Stale records can also degrade DNS server performance. A stale record may also prevent a computer from using a DNS domain name.
Scavenging is controlled through a combination of DNS server and zone properties.
|Zone properties||On the zone, enable scavenging and configure the following settings:
You can configure zone scavenging settings for all zones by right-clicking the server and selecting Set Aging/Scavenging for all zones.
|DNS server properties||Scavenging must be initiated to actually remove any records that have not been refreshed since the refresh interval has expired. To initiate scavenging:
Note: Scavenging is only configured on primary zones. After you enable scavenging on a zone, the zone file cannot be used on another DNS server.
Be aware of the following when configuring scavenging:
- Each DNS record has a default refresh setting. The record will attempt to refresh itself based on this interval. The default for an A record is 7 days.
- The no-refresh interval for the zone should be set with a value that is equal to (or less than) the longest record refresh interval.
- The refresh interval for the zone should be set to a value that is longer than the longest record refresh interval. If not, some records might be deleted before the record attempts to refresh itself.
- The difference between zone scavenging and server scavenging is that zone scavenging is applied to a single zone where server scavenging is applied to an entire server.