ddns add-delete operation

[Nagendra]

I have a query regarding DDNS-ADD operation. During the updation of
'A' type record in the nameserver, is it alright if we delete the
existing record in order to avoid ambiguity. The ambiguity comes into
picture in the following scenario:

before addition there is only 1 entry for the host of type 'A': 
test.xyz.com    10.116.10.10

after addition of a new A type record for the same host we have 2
entries:
test.xyz.com    10.116.10.10
test.xyz.com    10.116.10.20

And if we perform a query(nslookup) for test.xyz.com, we get the old
ip-adress (10.116.10.10) instead of the newly added. This problem
could be solved by deleting the existing 'A' type record for the
hostname before adding. But how safe is it to delete a record before
adding, because most of the nameservers do not give delete permission.


Also I would like to know the very purpose of having ambiguous records
in the nameserver.

Regards,
Nagendra