When deconfiguring the old DB console as described in "Using EMCA When the Database Host Name or IP Address Changes" with the following command:
emca -deconfig dbcontrol db command
And it fails, the following text is returned:
WARNING: EM is not configured for this database. No EM-specific actions can be performed. Some of the possible reasons may be:
There's a typo in the first option: "EM is configured with different hostname then physical host".
I think the typo also exists in previous EM versions.