Just one addition to Jeff's recap:

The filespace limit for accounts and groups does live in
the user volume set directory entries as well as in the
system volume set directory entries... Can be seen with
REPORT;ONVS=user_set and REPORT;ONVS=sys_vol_set.

I have seen customers using this to "force" users to stay
out of the system volume set disc space by setting the
filespace limit to zero on the system volume set directory
entry (ALTACCT;FILES=0) and to non-zero in the user volume
set directory entry (ALTACCT;FILES=nnn;ONVS=xxx).

This does not prevent a user from creating new groups
without an associated HOMEVS=xxx clause in such an account,
but the user won't be happy with it as it will refuse to
take files (until he decides to add NEWGROUP;ONVS and to
ALTGROUP;HOMEVS).

In short: most of the account/group attributes are taken
from the system directory (e.g. passwords, security etc),
but FILES(pace) is (also) taken from the user set directory.

:-) Lars