em 삭제하고 재 설치

Remove the following directories from your filesystem:
<ORACLE_HOME>/<hostname_sid>
<ORACLE_HOME>/oc4j/j2ee/OC4J_DBConsole_<hostname>_<sid>

sys로 접속하셔서
SQL> drop user sysman cascade;
SQL> drop role MGMT_USER;
SQL> drop user MGMT_VIEW cascade;
SQL> drop public synonym MGMT_TARGET_BLACKOUTS;
SQL> drop public synonym SETEMVIEWUSERCONTEXT;

emca -config dbcontrol db -repos create