class SecondConnection < ActiveRecord::Base

SecondConnection.establish_connection(
:adapter  => "informix",
:host     => "localhost",
:username => "hansnase",
:password => "very_secret",
:database => "ccdb@localhost"
)

self.abstract_class = true
end

“self.abstract_class = true” makes the thing actually work. Otherwise Rails seems to cache the database connection and does not switch back if you access any other classes but SecondConnection.

Yeah!

Later: Not so Yeah…

I had to establish another call to

  ActiveRecord::Base.establish_connection
       logger.info { "Establishing Base Connection" }
       log_connections

I assume it’s either an Informix problem or related to the old rails version I’m driving with.
Nevertheless: It works now.