response to SOA query was unsuccessful

[Ken Peng]

Hello,

I met a strange issue with adding a zone to BIND that I can't understand 
for, :)

I have two nameservers, say they are:

ns1.example.com
ns2.example.com

There are dozens of zones resolved by these two.

But, the zone example.com itself is resolved by registrar's DNS servers.
For example,

example.com.        10800   IN      NS      ns1.registrar.net.
example.com.        10800   IN      NS      ns2.registrar.net.

Now I want to change the zone to be resolved by ns1.example.com and 
ns2.example.com.

Before change the glues in registrar's control panel, I edited 
named.conf and added a zone file to /var/cache/bind/ for example.com, 
reload BIND in master. It seems fine. But when I tried to add a record 
to this zone via nsupdate, it got failed, the log shows:

[20150828142228] response to SOA query was unsuccessful

[20150828142228] response to SOA query was unsuccessful

[20150828142231] response to SOA query was unsuccessful

[20150828142231] response to SOA query was unsuccessful

Why this happens and how to fixup it? Thanks.

regards.