User Guide

Locking 77
Locking
You use the Locking page of the ColdFusion Administrator to configure automatic
mechanisms to protect shared data from incorrect access and corruption. In
addition, the
cflock tag provides granular control of simultaneous access to shared
data scope variables, including server, application, and session scopes. For more
information on the
cflock tag, see Developing ColdFusion Applications
Single threaded sessions
Single threading means that requests from a session occur sequentially. Each
request from the same session waits for previous requests to finish before
proceeding, thereby preventing multiple requests from simultaneously accessing
shared data. This option is disabled at installation.
Because session requests occur sequentially, single threaded sessions are useful if
you do not want to lock session scope variables with the
cflock tag. At the same
time, if you use frames in your ColdFusion application, each pane loads
consecutively. When single threaded sessions is enabled in the Administrator, you
do not need to the use the
cflock tag for session scope variables.
In addition, single threaded sessions can prove valuable to debugging a ColdFusion
application. If the application error goes away when single threaded sessions is
enabled. you likely have an unlocked session scope variable.
Variable scope locking settings
Specify variable scope lock settings by clicking an option. Scope (server, application
and session) settings are described in the following table:
Option Description
No automatic
checking or locking
No automatic checking or locking occurs. The developer must
protect variables with the cflock tag. If variables are not
locked, data corruption may result, and server instability may
occur.
Full checking ColdFusion Server checks shared variable scope access
automatically to ensure that it is properly locked. If a data read
or write occurs outside the scope of a
cflock tag, an error
displays.
Automatic read
locking
ColdFusion Server checks whether shared variable scope
writes are locked and automatically locks shared variable
scope reads. If ColdFusion Server encounters shared variable
scope writes that are not locked, an error displays.
install.book Page 77 Thursday, May 10, 2001 12:59 PM