ColdFusion MX provides four variable scopes, described in the following table, that let you maintain data that must be available to multiple applications or users or must last beyond the scope of the current request.
| Variable scope | Description |
|---|---|
Client |
Contains variables that are available for a single client browser over multiple browser sessions in an application. For information about browser sessions, see, What is a session?. Useful for client-specific information, such as client preferences, that you want to store for a significant period of time. Data is stored as cookies, database entries, or Registry values. Client variables can time out after an extended period. Although do not have to use the Client scope prefix in the variable name, code that uses the prefix is more efficient and easier to maintain. |
Session |
Contains variables that are available for a single client browser for a single browser session in an application. Useful for client-specific information, such as shopping cart contents, that you want to persist while the client is visiting your application. Data is stored in memory and times out after a period of inactivity or when the server shuts down. ColdFusion MX Administrator lets you select between two kinds of session management, Standard ColdFusion Session management and J2EE session management. For information about types of session management, see, ColdFusion and J2EE session management You must use the Session scope prefix in the variable name. |
Application |
Contains variables that are available to all pages in an application for all clients. Useful for application-specific information, such as contact information, that can vary over time and should be stored in a variable. Data is stored in memory and times out after a period of inactivity or when the server shuts down. You must use the Application scope prefix in the variable name. |
Server |
Contains variables that are available to all applications in a server and all clients. Useful for information that applies to all pages on the server, such as an aggregate page-hit counter. Data is stored in memory. The variables do not time out, but you can delete variables you create, and all server variables are automatically deleted when the server stops running. You must use the Server scope prefix in the variable name. |
The following sections provide information that is common to all or several of these variables. Later sections describe how to use the Client, Session, Application, and Server scopes in your applications, and provide detailed information about locking code.