problem about 'completion'

[Chihao Zhang]

I'm a new user to gnus, and when I started it for the first time (without
.newsrc generated), I press 'j' and then I can use 'tab' to prompt completion
 of all the names of groups on the server. But after I subscribed some of
the groups and started gnus again (with .newsrc generated), 'tab' can
only prompt the completion of the name of groups which I had
subscribed. How can I solve this and restore to have the completion of
all the groups on the server? Thx all.

-- 

           Chihao Zhang