The Active File
===============

   When Gnus starts, or indeed whenever it tries to determine whether
new articles have arrived, it reads the active file.  This is a very
large file that lists all the active groups and articles on the server.

   Before examining the active file, Gnus deletes all lines that match
the regexp `gnus-ignored-newsgroups'.  This is done primarily to reject
any groups with bogus names, but you can use this variable to make Gnus
ignore hierarchies you aren't ever interested in.  However, this is not
recommended.  In fact, it's highly discouraged.  Instead, *note New
Groups::. for an overview of other variables that can be used instead.

   The active file can be rather Huge, so if you have a slow network,
you can set `gnus-read-active-file' to `nil' to prevent Gnus from
reading the active file.  This variable is `t' by default.

   Gnus will try to make do by getting information just on the groups
that you actually subscribe to.

   Note that if you subscribe to lots and lots of groups, setting this
variable to `nil' will probably make Gnus slower, not faster.  At
present, having this variable `nil' will slow Gnus down considerably,
unless you read news over a 2400 baud modem.

   This variable can also have the value `some'.  Gnus will then
attempt to read active info only on the subscribed groups.  On some
servers this is quite fast (on sparkling, brand new INN servers that
support the `LIST ACTIVE group' command), on others this isn't fast at
all.  In any case, `some' should be faster than `nil', and is certainly
faster than `t' over slow lines.

   If this variable is `nil', Gnus will ask for group info in total
lock-step, which isn't very fast.  If it is `some' and you use an NNTP
server, Gnus will pump out commands as fast as it can, and read all the
replies in one swoop.  This will normally result in better performance,
but if the server does not support the aforementioned `LIST ACTIVE
group' command, this isn't very nice to the server.

   In any case, if you use `some' or `nil', you should definitely kill
all groups that you aren't interested in to speed things up.