auto_learn and use_bayes

[Peter Marshall]

When you use auto_learn it updates the bayes database right ?  If you 
have this in the main local.cf file, does it update the system wide 
bayes database or the local users ?  does "use_bayes" turn on system 
wide or individual ?

I guess, I would like to know how I know which is being used ?
How do I know it is running by each individual user (is this only 
through running sa-learn as that user).

How do I know it is running system wide ?  (is that through use_bayes 
and auto_learn).

If I run as a per user basis, do I need "use_bayes and auto_learn" in 
the local.cf ?  The man page says that auto_learn is good, but should be 
suplimented with sa-learn.  Just curious if auto_learn affecs all users 
bayes database, or the system one.

Sorry for all the questions this morning ... I am just a little confused ...
Peter