Variable: gnus-keep-backlog
gnus-keep-backlog is a customizable variable defined in gnus.el.gz.
Value
20
Documentation
If non-nil, Gnus will keep read articles for later re-retrieval.
If it is a number N, then Gnus will only keep the last N articles read. If it is neither nil nor a number, Gnus will keep all read articles. This is not a good idea.
Probably introduced at or before Emacs version 19.32.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/gnus.el.gz
(defcustom gnus-keep-backlog 20
"If non-nil, Gnus will keep read articles for later re-retrieval.
If it is a number N, then Gnus will only keep the last N articles
read. If it is neither nil nor a number, Gnus will keep all read
articles. This is not a good idea."
:group 'gnus-meta
:type '(choice (const :tag "off" nil)
integer
(sexp :format "all"
:value t)))