Viswa,
1.First of all, I will try to explain the scavenging settings.
As you may already know the scavenging can be set differently on the DNS server and zone properties. In the zone properties we have 2 sections.
No-refresh interval: During this period the client cannot update its record with the same IP address. The server rejects the request. (7 days by default). But it can always update its record with a new IP address which will resets time stamp of the record to the date and time .And a new No-refresh interval period will start.
Refresh interval: This period starts after the no-refresh interval period. During this period clients can update their records with the same IP or different IP. The server waits for any kind of update.
After these two periods finishes the records are set to scavenge on the next scavenge interval which is defined in the server level. And if the server level is not enabled, this means, that server will not scavenge records. Since the zone settings are replicated across Active Directory, the records can be scavenged through another DNS server. The recommendation for the environments where you have more than 5 DNS servers is, to set scavenging on 2 or 3 DNS server at most. If you dont limit the number of servers that carry out scavenging you will have great difficulty in troubleshooting missing records caused by the scavenging process. I have mainly seen this issue where:
a) You have DNS servers on poorly connected sites with questionable replication reliability
b) Permissions on the DNS record are stopping the client updating the record
2.DNS scavenging in Windows ,You can configure scavenging through a zone's properties.
Open the DNS console, right-click the zone, and choose Properties.
On the General tab, click Aging to open the Zone Aging/Scavenging Properties dialog box.
Set the Refresh Interval and the No-refresh Interval using the drop-down lists.
Select the Scavenge Stale Resource Records check box, and click OK to close both dialog boxes.
Apply globally
You can also configure scavenging for zones globally, rather than for an individual zone, by editing the server's properties. In the DNS console, right-click the server, and choose Set Aging/Scavenging For All Zones. The resulting dialog box is the same as that for an individual zone.
3.Also Ref the below posts for useful comments,
http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_22881595.htmlhttp://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_22881595.htmlhttp://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_23243719.html4.Best Practices on Windows DNS Scavenging
http://www.gilham.org/Blog/Lists/Posts/Post.aspx?List=aab85845%2D88d2%2D4091%2D8088%2Da6bbce0a4304&ID=211
