IXFR fallback to AXFR if diff is bigger than zone

[Klaus Darilion]

Hi!

I wonder how Bind as master handles IXFR when the requested IXFR would
be much than the AXFR. (For example: if you change the NSEC3 salt).

Are there some mechanisms to detect such a situation and trigger a
fallback to AXFR or will Bind always perform IXFR?

thanks
Klaus

PS: AFAIK the max journal size is 2 GB. In my case, the IXFR due to
NSEC3 salt changes is around 2.5GB. So actually I am surprised that such
big updates can be handled as IXFR.