When enabled (the default is disabled) unused dynamic dns records are periodically removed. This option should not be enabled for installations created with versions of samba before 4.9. Doing this will result in the loss of static DNS entries. This is due to a bug in previous versions of samba (BUG 12451) which marked dynamic DNS records as static and static records as dynamic. If one record for a DNS name is static (non-aging) then no other record for that DNS name will be scavenged. no