changing any dns server attribute bumps SOA serial

[Jeff Stevens]

I don't know the history here, but I am told the BIND 4 servers did not bump 
the serial when the zone attributes changed but only when the zone data 
changed, and I have a customer that is not happy his BIND 8 servers do zone 
transfers when he updates the attributes (no zone data changes).

What is the reason for the SOA now incrementing, so that I can respond to this?

Thank you...
-- 
Jeffrey Stevens