Oracle AS 10.1.2 SSO Failure - Unable to process request

" Oracle SSO Failure - Unable to process request
Either the requested URL was not specified in terms of a fully-qualified host name or OHS single sign-on is incorrectly configured. "

We his this error immediately after registering a Partner Application with Oracle As 10.1.2 Single Sign on. It took sometime for us to understand the problem & fix it.

The solution to the problem is detailed in the Metalink Note:311921.1. I'll just provide a brief summary here for people who do not have access to Oracle Metalink.

The URL used to register the Partner Application with Oracle As 10.1.2 Single Sign On contains the fully qualified hostname - with the domain name.

E.g: http://host.domain.com/osso_login_success

However, the URL used to test the application did not contain the fully qualified hostname - we even tried with the IP Address in the URL

E.g: http://host/osso_login_success

or

E.g: http://10.10.10.10/osso_login_success

Oracle As 10.1.2 Single Sign On mandates that the URL registered as the Partner Application should be only used. We cannot use any other URL formats to access the application.

We then tried with the URL:-

E.g: http://host.domain.com/myAppContext

We used the URL used in the registration in our browsers & it worked.