[otrs] Customer database + LDAP & customer login pages

Hello, the configuration of our OTRS 3.1.1 contains two customer backends - $Self->{CustomerUser} with LDAP - $Self->{CustomerUser1} with db backend the OTRS standard pages to reset the password or create a new account are not working, because they are using only the LDAP backend. Error Messages : OTRS-CGI-10[10804]: [Error][Kernel::System::CustomerUser::LDAP::SetPassword][Line:693]: Not supported for this module! OTRS-CGI-10[10724]: [Error][Kernel::System::CustomerUser::LDAP::CustomerUserAdd][Line:667]: Not supported for this module! ok, I can understand this error on a LDAP backend - but how can I force the modules to use the DB instead? Thanks for any idea Guido