Rebuild Oracle EM

A. On both nodes stop dbconsole
emctl stop dbconsole

B. Drop DBConsole manaully
Step 1: Drop AQ related objects in the SYSMAN schema Logon SQLPLUS as user. Bypass any errorSYSMAN
SQL> exec DBMS_AQADM.DROP_QUEUE_TABLE(queue_table=>'MGMT_NOTIFY_QTABLE',force =>TRUE);

Step 1:Logon SQLPLUS as user SYS or SYSTEM, and drop the sysman account and management objects:
SQL> exec DBMS_AQADM.DROP_QUEUE_TABLE(queue_table=>'SYSMAN.MGMT_NOTIFY_QTABLE',force =>TRUE);
SQL> EXEC sysman.emd_maintenance.remove_em_dbms_jobs;
SQL> EXEC sysman.setEMUserContext('',5);
SQL> REVOKE dba FROM sysman;
SQL> DECLARE
CURSOR c1 IS
SELECT owner, synonym_name name
FROM dba_synonyms
WHERE table_owner = 'SYSMAN';
BEGIN
FOR r1 IN c1 LOOPIF r1.owner = 'PUBLIC' THEN
EXECUTE IMMEDIATE 'DROP PUBLIC SYNONYM 'r1.name;
ELSE
EXECUTE IMMEDIATE 'DROP SYNONYM 'r1.owner'.'r1.name;
END IF;
END LOOP;
END;/
SQL> DROP USER mgmt_view CASCADE;
SQL> DROP ROLE mgmt_user;
SQL> DROP USER sysman CASCADE;
SQL> drop role MGMT_USER;
SQL> drop public synonym MGMT_TARGET_BLACKOUTS;
SQL> drop public synonym SETEMVIEWUSERCONTEXT;

Step 2: On both nodes remove the following directories from your filesystem
/_
/oc4j/j2ee/OC4J_DBConsole__
/_
/oc4j/j2ee/OC4J_DBConsole__

Step 3: Remove all files under ORACLE_BASE/cfgtoologs/emca/

C. Create DBConsole again. On node 80 run

emca -config dbcontrol db -repos create -cluster B

eofre run the command you should verify the following information:

Cluster Name. To finde this name run:
$ cd $CRS_HOME/bin
$ ./cemutlo -n

Database unique name. To finde this name run:
SQL> show parameter db_unique_name
Listener port
SYS password
DBSNMP password
In case you have ASM you should know:
ASM ORACLE_HOME
ASM SID
ASM ROLE
ASM USERNAME
ASM PORT

For more details check:
How to manage DB Control 11.x for RAC Database with emca (Doc ID 578011.1)

If any error please upload ORACLE_BASE/cfgtoologs/emca/