gnus-save-startup-file-via-temp-buffer

gnus-save-startup-file-via-temp-buffer is a variable defined in `gnus-start.el'.
Its value is

t

Documentation:
Whether to write the startup file contents to a buffer then save
the buffer or write directly to the file. The buffer is faster
because all of the contents are written at once. The direct write
uses considerably less memory.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.