emdb.nohup: XML-20108: (Fatal Error) Start of root element expected ement expected

oracle@dbt1.ro:/home/oracle>emctl start dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.
https://dbt1.ro:5501/em/console/aboutApplication
Starting Oracle Enterprise Manager 11g Database Control ............................................................................................. failed.

oracle@dbt1.sniep.ro:/oracle/app/db/product/11.2.0/dbt1_repoimt/sysman/log>tail -f emdb.nohup
14/07/28 17:51:28 Fatal error: server exiting
----- Mon Jul 28 17:51:30 2014::Checking status of DBConsole : 42074202 -----
----- Mon Jul 28 17:51:30 2014::DBConsole exited at Mon Jul 28 17:51:30 2014 with return value 1. -----
----- Mon Jul 28 17:51:30 2014::Restarting DBConsole. -----
----- Mon Jul 28 17:51:30 2014::Console Launched with PID 42074206 at time Mon Jul 28 17:51:30 2014 -----
----- Mon Jul 28 17:51:30 2014::osname is aix -----
----- Mon Jul 28 17:51:31 2014::heap size used is 384M -----
----- Mon Jul 28 17:51:31 2014::perm size used is -1 -----
----- Mon Jul 28 17:51:31 2014::joptions used are -Xmx384M -----
WARNING: Ignoring zero-length code source: /oracle/app/db/product/11.2.0/jdk/jre/lib/ext/ldapsec.jar(from system property java.ext.dirs)
WARNING: Unable to access loaded classes.
14/07/28 17:51:33 Error initializing server: /oracle/app/db/product/11.2.0/oc4j/j2ee/OC4J_DBConsole_dbt1_repoimt/config/server.xml, Fatal error at line 1 offset1 in file:/oracle/app/db/product/11.2.0/oc4j/j2ee/OC4J_DBConsole_dbt1_repoimt/config/server.xml: .<Line 1, Column 1>: XML-20108: (Fatal Error) Start of root element expected.

14/07/28 17:51:33 Fatal error: server exiting

This can happen after one of the following:

- DB was upgraded and a patchset was applied.
- The server experienced a disk full issue

Option 1

Restore the file from a binary backup or another similar installation (same OS and DB version) or from a new similar fresh installation.

This option worked for me:

oracle@dbt1.ro:/home/oracle>cp /oracle/app/db/product/11.2.0/oc4j/j2ee/OC4J_DBConsole_dbt1_repoimt/config/server.xml /oracle/app/db/product/11.2.0/oc4j/j2ee/OC4J_DBConsole_dbt1_repbit/config/server.xml

oracle@dbt1.ro:/home/oracle>more /oracle/app/db/product/11.2.0/oc4j/j2ee/OC4J_DBConsole_dbt1_repbit/config/server.xml 

oracle@dbt1.ro:/home/oracle>emctl start dbconsole

Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0

Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.

https://dbt1.ro:5502/em/console/aboutApplication

Starting Oracle Enterprise Manager 11g Database Control ............................ started.

------------------------------------------------------------------

Logs are generated in directory /oracle/app/db/product/11.2.0/dbt1_repbit/sysman/log

There is also the second option with reconfiguration of EM dbconsole

Rebuild the configuration files for the DB Console:

- Stop DB Console processes: emctl stop dbconsole
- deconfig the DB Console: emca -deconfig dbcontrol db
- reconfig the DB Console: emca -config dbcontrol db