You can manipulate the zone data after you switch the server to Read-Write mode.
You cannot modify imported DNS zone data or server-level settings in Address Manager while the Managed Windows server is in Read-Only mode. This ensures consistency between the data on the Managed Windows server and its representation in Address Manager.
Note: It is still possible to add resource records to a Read-Only zone using the Bulk DNS Import
feature. To return the zone data to a consistent state with that of the Windows DNS server,
re-import DNS and select the Re-import Resource Records check box.