RedirectChannel is the subdirectory under the /var/opt/SUNWportal/portals/<portal_id>/desktop/welcome_sample/ directory. There are three other subdirectories such as aml, chtml, and wml under RedirectChannel. All these subdirectories contain the content.jsp.
The JSP available in the welcome_sample directory and its description is:
This JSP redirects the user to the Portal welcome page.