MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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326 Chapter 15: Using Persistent Data and Locking
Exporting the client variable database
If your client variable database is stored in the Windows system Registry and you need to move it
to another machine, you can export the Registry key that stores your client variables and take it to
your new server. The system Registry lets you export and import Registry entries.
To export your client variable database from the Registry in Windows:
1
Open the Registry editor.
2
Find and select the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\ColdFusion\CurrentVersion\
Clients
3
On the Registry menu, click Export Registry File.
4
Enter a name for the Registry file.
After you create a Registry file, you can copy it to a new machine and import it by clicking
Import Registry File on the Registry editor Registry menu.
Note: On UNIX systems, the Registry entries are kept in /opt/coldfusion/registry/cf.registry, a text file
that you can copy and edit directly.
Configuring and using session variables
Use session variables when you need the variables for a single site visit or set of requests. For
example, you might use session variables to store a user’s selections in a shopping cart application.
(Use client variables if you need a variable in multiple visits.)
Caution: To preserve data integrity, put code that uses session variables inside
cflock
tags. For
information on using cflock tags see “Locking code with cflock” on page 333 .
What is a session?
A session refers to all the connections that a single client might make to a server in the course of
viewing any pages associated with a given application. Sessions are specific to both the individual
user and the application. As a result, every user of an application has a separate session and has
access to a separate set of session variables.
This logical view of a session begins with the first connection to an application by a client and
ends after that client's last connection. However, because of the stateless nature of the web, it is
not always possible to define a precise point at which a session ends. A session should end when
the user finishes using an application. In most cases, however, a web application has no way of
knowing if a user has finished or is just lingering over a page.
Therefore, sessions always terminate after a time-out period of inactivity. If the user does not
access a page of the application within this time-out period, ColdFusion interprets this as the end
of the session and clears any variables associated with that session.
The default time-out for session variables is 20 minutes. You can change the default time-out on
the Memory Variables page of the ColdFusion MX Administrator Server tab.
You can also set the time-out period for session variables inside a specific application (thereby
overruling the Administrator default setting) by using the
cfapplication
tag
sessionTimeout
attribute. However, you cannot use the
cfapplication
tag to set a time-out value that is greater
than the maximum session time-out value set on the Administrator Memory Variables page.
Your application can also manually end a session, for example, when a user logs out.