The TRACE HTTP method is designed as a debug feature as follows: whatever you send the remote server as an HTTP request, the remote server will loop-back that data and send it all back to you. That allows you to see if it is receiving all the data it should (e.g. that data isn't being corrupted by a proxy). It could, in theory, be used as a first step towards debugging a Web application if you think your application is going wrong because it isn't receiving the correct headers - however, I don't think I've ever used it in practise because it's only marginally more difficult to get the Web app itself to output the headers it receives to a log (e.g. by addition of a Filter). Also it has been found that a server which allows TRACE has a minor security flaw (see
Cross-Site Tracing Issues) so many admins disable it for that reason.
There's also a handy script online that will show you the results of a TRACE:
http://schroepl.net/cgi-bin/http_trace.pl .
Note: You won't be expected to know anything (significant) about TRACE for the SCWCD!
Charles Lyons (SCJP 1.4, April 2003; SCJP 5, Dec 2006; SCWCD 1.4b, April 2004)
Author of OCEJWCD Study Companion for Oracle Exam 1Z0-899 (ISBN 0955160340 / Amazon Amazon UK )