C:\Documents and Settings\Administrator.sriram>emctl getemhome
Oracle Enterprise Manager 10g Database Control Release 10.2.0.1.0
Copyright (c) 1996, 2005 Oracle Corporation.  All rights reserved.
EMHOME=D:\oracle\xxxxxx/machine_name.domailname_ORACLE_SID

So i have already configured Dbcontrol......But

C:\Documents and Settings\Administrator.sriram>emctl  status dbconsole
Unable to determine local host from URL REPOSITORY_URL=http://sriram.domainname:%EM_UPLOAD_PORT%/em/
upload/
 .

set ORACLE_HOME=<your_oracle_home_name>
set ORACLE_SID=<your_sid_name>
 
emca -config dbcontrol db -repos recreate

Z:\>emca -config dbcontrol db -repos recreate
Incorrect usage:

C:\>emca -config dbcontrol db -repos recreate

STARTED EMCA at Jun 23, 2009 2:35:58 PM
EM Configuration Assistant, Version 10.2.0.1.0 Production
Copyright (c) 2003, 2005, Oracle.  All rights reserved.

Enter the following information:
Database SID: orcl
Database Control is already configured for the database orcl
You have chosen to configure Database Control for managing the database orcl
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 port number: 1521
Password for SYS user:
Password for DBSNMP user:
Password for SYSMAN user:
Email address for notifications (optional):
Outgoing Mail (SMTP) server for notifications (optional):
-----------------------------------------------------------------

You have specified the following settings

Database ORACLE_HOME ................ D:\oracle\product\10.2.0\db_1

Database hostname ................ sriram
Listener port number ................ 1521
Database SID ................ orcl
Email address for notifications ...............
Outgoing Mail (SMTP) server for notifications ...............

-----------------------------------------------------------------
Do you wish to continue? [yes(Y)/no(N)]: y
Jun 23, 2009 2:36:54 PM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at D:\oracle\product\10.2.0\db_1\cfgtoollogs\emca\orcl\emca_2009-06-23_02-35-57-PM.log.
Jun 23, 2009 2:36:59 PM oracle.sysman.emcp.util.PortManager isPortInUse
WARNING: Specified port 5540 is already in use.
Jun 23, 2009 2:36:59 PM oracle.sysman.emcp.util.PortManager isPortInUse
WARNING: Specified port 5520 is already in use.
Jun 23, 2009 2:36:59 PM oracle.sysman.emcp.util.PortManager isPortInUse
WARNING: Specified port 5500 is already in use.
Jun 23, 2009 2:36:59 PM oracle.sysman.emcp.util.PortManager isPortInUse
WARNING: Specified port 1830 is already in use.
Jun 23, 2009 2:36:59 PM oracle.sysman.emcp.util.DBControlUtil stopOMS
INFO: Stopping Database Control (this may take a while) ...
Jun 23, 2009 2:38:39 PM oracle.sysman.emcp.EMReposConfig dropRepository
INFO: Dropping the EM repository (this may take a while) ...
Jun 23, 2009 2:38:43 PM oracle.sysman.emcp.EMReposConfig invoke
INFO: Repository successfully dropped
Jun 23, 2009 2:38:44 PM oracle.sysman.emcp.EMReposConfig createRepository
INFO: Creating the EM repository (this may take a while) ...
Jun 23, 2009 2:38:45 PM oracle.sysman.emcp.EMReposConfig invoke
SEVERE: Error creating the repository
Jun 23, 2009 2:38:45 PM oracle.sysman.emcp.EMReposConfig invoke
INFO: Refer to the log file at D:\oracle\product\10.2.0\db_1\cfgtoollogs\emca\orcl\emca_repos_create_<date>.log for more details.
Jun 23, 2009 2:38:45 PM oracle.sysman.emcp.EMConfig perform
SEVERE: Error creating the repository
Refer to the log file at D:\oracle\product\10.2.0\db_1\cfgtoollogs\emca\orcl\emca_2009-06-23_02-35-57-PM.log for more details.
Could not complete the configuration. Refer to the log file at D:\oracle\product\10.2.0\db_1\cfgtoollogs\emca\orcl\emca_2009-06-23_02-35-57-PM.log for
 more details.

C:\>D:\oracle\product\10.2.0\db_1\cfgtoollogs\emca\orcl\emca_2009-06-23_02-35-57-PM.log

C:\>set oracle_sid=orcl


C:\>emctl status dbconsole
Oracle Enterprise Manager 10g Database Control Release 10.2.0.1.0
Copyright (c) 1996, 2005 Oracle Corporation.  All rights reserved.
http://sriram:5500/em/console/aboutApplication
Oracle Enterprise Manager 10g is not running.
------------------------------------------------------------------
Logs are generated in directory D:\oracle\product\10.2.0\db_1/sriram_orcl/sysman/log

C:\>emctl start dbconsole
Oracle Enterprise Manager 10g Database Control Release 10.2.0.1.0
Copyright (c) 1996, 2005 Oracle Corporation.  All rights reserved.
http://sriram:5500/em/console/aboutApplication
Starting Oracle Enterprise Manager 10g Database Control ...The service name is invalid.

More help is available by typing NET HELPMSG 2185.


C:\>NET HELPMSG 2185

The service name is invalid.


EXPLANATION

You tried to start a service that is not configured on this system.

ACTION

Check the spelling of the service name or
check the configuration information for the service using the Services option from Server Manager.


 At the  log [QUOTE] ORA-20001: SYSMAN already exists..
ORA-06512: at line 17
[/QUOTE]

drop user sysman cascade;
drop public synonym SETEMVIEWUSERCONTEXT;
drop role MGMT_USER;
drop PUBLIC SYNONYM MGMT_TARGET_BLACKOUTS;
drop user MGMT_VIEW;

And then,

emca -deconfig dbcontrol db
emca -config dbcontrol db -repos create


Its working now.