Resolution
fact
Domain Migration Administrator 7.x
symptom
The USN is updated on accounts that are not migrated.
cause
Domain Migration Administrator will only replace and update conflicting  accounts in the target, if the account in the target has the same sAMaccountName as the source account. As a result, the properties of the target are overwritten by the properties from the source. If a property is not defined in the source, the target account will keep its current value. This is why the 'USN' is incremented (as displayed by running an ADSI Edit on the target account), as every account selected in the project will have a read operation run against it to determine if the target property differs from that same property in the source.
Domain Migration Administrator 7.x
symptom
The USN is updated on accounts that are not migrated.
cause
Domain Migration Administrator will only replace and update conflicting  accounts in the target, if the account in the target has the same sAMaccountName as the source account. As a result, the properties of the target are overwritten by the properties from the source. If a property is not defined in the source, the target account will keep its current value. This is why the 'USN' is incremented (as displayed by running an ADSI Edit on the target account), as every account selected in the project will have a read operation run against it to determine if the target property differs from that same property in the source.
Additional Information
Formerly known as NETIQKB19419