DNS/BIND/9.12-release-noteについて、ここに記述してください。

https://ftp.isc.org/isc/bind9/9.12.0/RELEASE-NOTES-bind-9.12.0.pdf 

Many aspects of named have been modified to improve query performance,  and in particular,
performance for delegation-heavy zones:
–
The additional cache ("acache") was found not to significantly improve performance and has
been removed. As a result, the acache-enable and acache-cleaning-interval options no longer
have any effect. For backwards compatibility, BIND will accept their presence in a configura-
tion file, but will log a warning.
–
In place of the acache,named can now use a glue cache to speed up retrieval of glue records
when sending delegation responses.  Unlike acache, this feature is on by default; 
 use glue-cache no; to disable it.

–  minimal-responses is now set to no-auth-recursive by default.
–
The additional-from-cache and additional-from-auth options no longer have any effect.
named will log a warning if they are set.

–
Several functions have been refactored to improve performance, including name compres-
sion, owner name case restoration, hashing, and buffers.
–
When built with default configure options,
named no longer fills memory with tag values
when  allocating  or  freeing  it.   This  improves  performance,  but  makes  it  more  difficult  to
debug certain memory-related errors. The default is reversed if building with developer options.
named -M fill
or
named -M nofill
will set the behavior accordingly regardless of build
opti

300ページ以上! ftp://ftp.nominum.com/pub/isc/bind9/9.12.1b1/doc/arm/Bv9ARM.pdf