The Database Maintenance utility displays a message if users are connected to the selected database, and enables notification of these users through the Connected Users dialog box, which displays connected users in a list. Notify the users to log off the database by using either the default message or creating a unique message, and clicking Send.
Avoid performing maintenance on a database that has connected users, because it may result in system instability on the local machine. If the choice is to wait, use the Refresh List button to get a current view of connected users.