Re configure the Enterprise Manager (em console)

First of all you need to  de-configure the emctl repository

emca -deconfig dbcontrol db -repos drop


This will ask for your

•  Database SID
•  LISTNER Port Number
•  Passwords for SYS 
•  Passwords for SYSMAN

Then you have to re configure the  emctl repository

emca -config  dbcontrol db -repos create

This will ask for your

• Database SID
• ORACLE_HOME
• Passwords for SYS
• Passwords for DBSNMP
• Passwords for SYSMAN
• Email for notification for Alerts (Optional)
• Outgoin SMTP email for Alerts (Optional)

Now you  have newly created emca repository  :)

now  start  enterprise manager service.

emctl start dbconsole