About Portlet Preferences
Portlet preferences store values that can be used to define the behavior or appearance of a portlet. You can access a preference through the use of binding expressions. Preferences can be persisted through the use of scopes on a per user basis, meaning that each individual user has a separate preference value for each portlet instance. Composite Application Framework (CAF) provides several preference scope extensions for persisted values:
Value stored per portlet instance
This scope extension enables storing different instances of the portlet on different portal pages with their own values. All users who access the portlet instance can see the same value. This scope extension is useful when wiring and linking portlets. This is the default portlet persistence preference setting in CAF.
Value shared by all portlet instances
All instances of the portlet share the same value. This changes the preference value into a static variable. Use this scope when the preference is a configuration parameter that does not vary between portlet instances.
Transient session value
The transient session value is stored for an individual user until that user logs out of the portal session or until the portlet bean scope expires.