Tracing, and the need to trace your application, can come from many different areas. As a developer, tracing an application can be a quicker alternative than resorting to a full debugger when you are trying to diagnose a problem. Tools like DTrace can be even more intrusive and retrieve some very specific, and extensive, information about your application.
For administrators, tracing provides the only method for locating and finding the information that you need to diagnose problems. Without access to the source code, tracing is often your only means of determining what an application is doing. This tutorial showed that with tracing alone, you can find and diagnose problems with just a few commands.