secondary zone removing

[Alexis Albinet]

Hi,

I've two questions :

when I delete a dns domain on my primary server, should I restart (stop
then start) the bind server in order to make the server  to not answer
to this deleted domain. In fact, is restarting  server cleaning the
cache ??

my second problem is that:
When I remove a secondary zone entry in named.conf, should this zone be
deleted automatically on the disk by a reload or a restart of named ?

tks in advance.
Alex