854 8.8 Free and busy
to Exchange 2007 store the data used by clients to calculate when users
are available in a public folder, but Exchange 2007 introduces the new
Availability Service to replace the need to hold data in a public folder in
favor of direct publication of free and busy data by Outlook 2007 clients
as properties of user mailboxes. However, it is going to take some time
before any organization is able to deploy Exchange 2007 everywhere, so
we will have to deal with the public folder-based implementation for
quite some time to come.
Outlook is responsible for updating the data in the public folder and
does so according to user-speciﬁc options as shown in Figure 8.50. The
default is for Outlook to connect and update free and busy data every 15
minutes and to publish 2 months of availability data. In other words, if
every user in the organization uses the default publication options, you will
not be able to see the availability of another user’s calendar past the next 2
months, even if they have scheduled meetings and other appointments past
that time. You can publish a maximum of 36 months free and busy data
and update the server as often as every minute.
Free and busy data describes when a user is busy over a period of time
but does not hold any other information, such as whether they are at a
meeting or have a personal appointment, the location, or any other indica-
tion of why they might be busy. Thus, when you view another user’s calen-
dar and see that they are busy between 10
AM and 5PM, the time might be
taken up by one long appointment or occupied by several shorter meetings.
In addition, the items in the other user’s calendars may have different status
such as busy or tentative. Essentially, Exchange treats any slot that a user
creates in their calendar as busy and any that is vacant as free.