OEM Reconfiguration

Problem 

Database is registered with a new listener (LISTENER2) working at port 1522 instead of 1521. The original listener remains intacted but the database is not registered there anymore.

Result 

OEM does not work anymore

Fix

It looks like following step should be enough:

emca -reconfig ports -PORT 1522

However the updated configuration does not work for the new listener name, the following step helps:

emca -deconfig dbcontrol db -repos drop
emca -config dbcontrol db -repos create
or
emca -deconfig dbcontrol db
emca -config dbcontrol db -repos recreate

Useful

A HTTP port where OEM is listening, set ORACLE_SID then run a following command:
[oracle@if1 ~]$ emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.
https://if1:5501/em/console/aboutApplication
Oracle Enterprise Manager 11g is running.

Literature

1. Oracle® Database Installation Guide 10g Release 2 (10.2) for Linux x86 - Appendinx E. Managing Oracle Database Port Numbers, Section E.5 Changing Oracle Enterprise Manager Database Console Ports.
2. Oracle® Database Administrator's Guide 11g Release 2 (11.2) -
   EMCA Troubleshooting Tips