Recreating the OEM .

Recreating the Oracle Enterprise Manager (OEM) for your newly duplicated database.
Enterprise Manager Grid Control - Version: 10.1.0.2 to 11.2.0.2 - Release: 10.1 to 11.2

If there is a change in SID, DBID, or hostname for the database that has been restored then you need to recreate the dbconsole.

Refer How To Reconfigure DB Control After a Hostname, Domain name or Listener Change Has Occurred On The Server
(MOS Doc ID 293678.1) Information in this document applies to any platform.

This is the process:

Stop OEM

# emctl stop dbconsole

Drop the existing OEM installation.

# cd $ORACLE_HOME
# cd ./sysman/admin/emdrep/bin/
#./RepManager servername.domain.com 1526 dev311 -action drop

Enter SYS user's password :
Enter repository user name : sysman
Getting temporary tablespace from database...
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.
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Dropping Repos User ... Done.
Dropping Roles/Synonymns/Tablespaces ... Done.
Dropped Repository Successfully.

Install the OEM

# cd $ORACLE_HOME/bin
./emca -config dbcontrol db -repos create

STARTED EMCA at Apr 12, 2012 2:26:40 PM
EM Configuration Assistant, Version 11.2.0.0.2 Production
Copyright (c) 2003, 2005, Oracle. All rights reserved.

Enter the following information:
Database SID: dev311
Database Control is already configured for the database dev311
You have chosen to configure Database Control for managing the database dev311
This will remove the existing configuration and the default settings and perform a fresh configuration
Do you wish to continue? [yes(Y)/no(N)]:y

Listener ORACLE_HOME [ /app/oracle/product/11.2.0 ]:
Password for SYS user: xxxx
Password for DBSNMP user: xxxx
Password for SYSMAN user: xxxxx
Email address for notifications (optional): email@company.com
Outgoing Mail (SMTP) server for notifications (optional): smtp-server.com

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

You have specified the following settings

Database ORACLE_HOME ................ /app/oracle/product/11.2.0.2

Local hostname ................ servername.com
Listener ORACLE_HOME ................ /app/oracle/product/11.2.0.2
Listener port number ................ 1526
Database SID ................ dev311
Email address for notifications ............... email@company.com
Outgoing Mail (SMTP) server for notifications ............... smtp-server.com

-----------------------------------------------------------------
Do you wish to continue? [yes(Y)/no(N)]: y
Apr 12, 2012 2:28:25 PM oracle.sysman.emcp.EMConfig perform
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***********************************************************
Enterprise Manager configuration completed successfully
FINISHED EMCA at Apr 12, 2012 2:34:42 PM

I like to finish up with a stop and start of the emctl services.

# emctl stop dbconsole

# emctl start dbconsole

Using my browser I can access OEM and review my newly cloned database.