OpenEdge Application Server:<br />Developing AppServer Applications Understanding condition handling in distributed Progress 4GL sessions

The processing boundary that exists between a Progress 4GL client application session and an AppServer session influences how error conditions are viewed and handled in each session. Table 4–9 defines the four basic Progress 4GL conditions and describes how raising these conditions in one session affects the processing in the other, associated session.

Table 4–9: Progress 4GL conditions
Condition	Description
ERROR	An unhandled `ERROR` condition raised in a client application has no effect on any of the AppServer agents to which it is connected. Conversely, an unhandled `ERROR` condition raised in an AppServer agent has no effect on the client application to which it is connected. Handling this condition conforms to standard Progress 4GL rules. For more information about these rules, see OpenEdge Development: Progress 4GL Handbook . The only way an AppServer session can raise `ERROR` in the client application is for a remote procedure or an Activate procedure to execute the `RETURN` `ERROR` statement. This raises `ERROR` on the `RUN` statement in the client application.
ENDKEY	An unhandled `ENDKEY` condition raised in a client application has no effect on any of the AppServer agents to which it is connected. Conversely, an unhandled `ENDKEY` condition raised in an AppServer agent has no affect on the client application to which it is connected. Handling this condition conforms to standard Progress 4GL rules. For more information about these rules, see OpenEdge Development: Progress 4GL Handbook . An AppServer session raises the `ENDKEY` condition if an attempt to find a database record fails or an `INPUT` `FROM` statement reaches the end of an input stream. Like a batch client, there are no user-interface events that can raise the `ENDKEY` condition.
STOP	A `STOP` condition raised in a client application while it is executing a remote procedure causes a `STOP` condition to be raised in the context of the executing procedure in the AppServer session. An unhandled `STOP` condition in an AppServer session results in the request being returned with the `STOP` condition. On a root client application, an unhandled `STOP` condition causes OpenEdge to restart the client Startup Procedure (`-p`). This restarted session retains connections with databases, but deletes outstanding persistent procedures. This restart also disconnects any AppServer agents it is connected to and deletes active remote persistent procedures. In an AppServer agent, an unhandled `STOP` condition causes the `STOP` condition to be propagated back to the client application where it is raised again in the context of the outstanding remote procedure request. It does not cause a restart of the AppServer session. All active remote persistent procedures and AppServer agent connections remain intact.
QUIT	An unhandled `QUIT` condition raised in a client application disconnects the client application from all AppServer agents it is connected to and deletes the proxy persistent procedure handles for that client application. An unhandled `QUIT` condition raised in an AppServer session results in the immediate, successful completion of the current remote procedure request. The client application is then automatically disconnected from the AppServer agent.