If you run Emacs on a machine locally, and get your news from a machine over some very thin strings, you want to cut down on the amount of data Gnus has to get from the server.
gnus-read-active-filenil, which will inhibit Gnus from
requesting the entire active file from the server. This file is
often very large. You also have to set
gnus-check-new-newsgroups and
gnus-check-bogus-newsgroups to nil to
make sure that Gnus doesn't suddenly decide to fetch the active
file anyway.gnus-nov-is-evilnil (which is the
default). If, for example, you wish to not use
NOV (see Terminology) with the
nntp back end (see Crosspost
Handling), set nntp-nov-is-evil to a
non-nil value instead of setting this. But you
normally do not need to set nntp-nov-is-evil
since Gnus by itself will detect whether the
NNTP server supports
NOV. Anyway, grabbing article headers from
the NNTP server will not be very fast if
you tell Gnus not to use NOV.
As the variables for the other back ends, there are
nndiary-nov-is-evil,
nndir-nov-is-evil,
nnfolder-nov-is-evil,
nnimap-nov-is-evil,
nnml-nov-is-evil, and
nnspool-nov-is-evil. Note that a
non-nil value for gnus-nov-is-evil
overrides all those variables.