When you encounter a problem with your application, whether during compilation or at run time, the first step is to gather diagnostic information to locate the cause of the problem. The source of a problem typically is in one of two places: the server web application, or the client application.

Flex includes several different logging and error reporting mechanisms that you can use to track down failures:

Client-side logging and debugging 

With the debugger version of Adobe® Flash® Player, or with an AIR application that you debug using ADL, you can use the global trace() method to write out messages or configure a TraceTarget to customize log levels of applications for data services-based applications. For more information, see Client-side logging and debugging.

Compiler logging 

When compiling your Flex applications from the command line and in Adobe® Flex® Builder®, you can view deprecation and warning messages, and sources of fatal errors. For more information, see Compiler logging.

Web-tier logging 

The Flex module for Apache and IIS compiler has its own logging facilities. For more information, see Using the web-tier compiler log files.

The following example shows the types of logging you can do in the appropriate environment:

To use client-side debugging utilities such as the trace() global method and client-side data services logging, you must install and configure the debugger version of Flash Player. This is described in Using the debugger version of Flash Player. The debugger version of Flash Player is not required to log compiler messages or web-tier compiler messages.