How to make transition between two Domains

[Rahul Parasnis]

Hello All, 

I have a domain a.b.c domain my Server is forwarding it to the Firewall 
on which there is another DNS Server running who knows internet root Servers.

Now I would like to change this to 

country.company   where ".company"  is my new Root Server.
That Means I will be primary for country.company Zone.and My root Server is
.company
In this New Structure I will be resolving internet names through Proxy
server and Currently for a.b.c domain I am forwarding it to the DNS Server
running on Firewall.


So If I want to resolv names in another country. i.e
another-country.company, then I will be getting  information of who is
authoritative for "another-country.company" from ".company" root Server .
Please correct me if I am wrong !!

As I told you before the Internet Name Resolution will be done by Proxy
Server. 

Now in order to do this transition, I will set up country.company as
Primary Master.

My question is ,what is the Good Solution to move from a.b.c domain to
country.company domain? 

1. like in a one go i.e change all clients resolv.conf ( This will be very
dangerous If something goes wrong ) 
2. Phase by Phase. ( Removing some clients from a.b.c and putting it in
country.company) 

In this second option , if  I change some clients pointing towards new
"country.company" server and 
rest are looking for a.b.c then how the clients resolver of a.b.c will find
a host in country.company ? 
search directive will work with one parent domain not like following , am I
right ? 
search a.b.c country.company
3.   Remove first all clients from a.b.c and the Resolution will be done
locally, and then Start putting it in new Domain.

Please give me your Ideas about what could be the good solution for this
Transition 

Thanks and Regards

- Rahul Parasnis