Robert,
 
You'll get the 'disk quota exceeded' message on the filer when the user attempts write & the write will fail.
What you might consider, to make life easier all around, is a blanket message to your users, if that's feasible, and request the users clean house prior to the quotas invocation. Then identify the users who ignored your request and add them to your quotas file at, or slightly above, their current use. After they've responded and cleaned-up below the quota, remove the special entries.
 
Example (quota entries for user home directories):
/vol/users            tree                          50G    500K    #user volume
*                          user@/vol/users        100M    3K       #quotas for all users
joe                        user@/vol/users       1500K    3K    #transgressor
beth                      user@/vol/users        2600K    4K    #transgressor
 
Of course, this path of action is much easier if most users clean-up below the intended quotas.
 
Regards,
Bob Francett
BP Exploration Alaska
-----Original Message-----
From: Robert Wiebke [mailto:wiebke@lucent.com]
Sent: Wednesday, May 09, 2001 11:02 AM
To: toasters@mathworks.com
Subject: Quotas

We're looking to retroactively implement a 100mb quota on most of our users.  Many of these users are are above 100mb at the moment.  My question is how does Filer treat a new quota if the user is already above the specified quota?
 
Will it fail, or just not allow any more writes to disk?  I looked on the NOW site but I could not seem to find an answer to this question. 
Thanks in advance.