[Samba] DNS state after upgrading samba

[henri transfert]

Hello,

I am in the process of upgrading one single DC (internal DNS) to 4.8.12.

I have followed the procedure of adding a new DC, transfert FSMO roles and
demote the old DC.
Everything gone right (except at the tranfert FSMO step where I faced the
problem described here
https://lists.samba.org/archive/samba/2017-August/210140.html , this bug
subsists in 4.8.12 , maybe it has been fixed in later release ? At the end
, I have all roles transfered ok to the new DC).

After the demote step, I followed the wiki
https://wiki.samba.org/index.php/Demoting_a_Samba_AD_DC#Verifying_the_Demotion
, and manually deleted all references to the old DC from the DNS manager.
Nevertheless, I still have some references to the old DC in the Forward
Lookup Zone:"(same as parent folder) Start Of Authority" and "(same as
parent folder) Name Server .
I only have a "Properties" menu for these entries, so I cannot delete these
manually.

I have the same entries in the _msdcs , and Reverse Lookup Zone.

First question :
How can I delete these entries to remove any reference to the old DC ?

Second question :
I have only one SOA entry, and this one refers to the old DC. Is it safe to
manually modify its properties with the new DC data ? If not how can I
correct this ?

Thanks  in advance for your help.

Henri