When adding a new server type using the new server wizard from the the server perspective in eclipse, this error message will be shown. (this happens only if we are adding a new server of same type of old server)
To get rid from this, goto->windows->preferences->server->run time environment-> delete the tomcat instance from there and then add the new instance here.
To get rid from this, goto->windows->preferences->server->run time environment-> delete the tomcat instance from there and then add the new instance here.