Clean up after failure installation of EM 12c cloud control

When fails half way during installation of 12c Cloud Control, of course, we'd better to check logs under /u01/app/oraInventory/logs/emdbprereqs/LATEST to understand what is going wrong.
e.g
Executing Prereq Action
-----------------------------
executing Action: SELECT COUNT(1) FROM ALL_USERS WHERE USERNAME in ('SYSMAN_MDS', 'MGMT_VIEW', 'SYSMAN_BIP','SYSMAN_APM','BIP', 'SYSMAN_OPSS', 'SYSMAN_RO')
output: 1

Prerequisite failed

After fix the issue mentioned in log files, in order to re-install it, other than follow "15 Deinstalling Enterprise Manager (Single and Multi-OMS Environments)" in Oracle® Enterprise Manager Cloud Control Advanced Installation and Configuration Guide
12c Release 2 (12.1.0.2).

Next, we also need to drop objects created in repository database.

Below commands may help.

select count(1) from dba_synonyms where table_owner in ('SYSMAN','SYSMAN_MDS','MGMT_VIEW','SYSMAN_BIP','SYSMAN_APM','BIP','SYSMAN_OPSS','SYSMAN_RO')
-- Generate drop synonyms scripts
select 'drop public synonym '|| synonym_name || ' ;'  from dba_synonyms where table_owner in ('SYSMAN','SYSMAN_MDS','MGMT_VIEW','SYSMAN_BIP','SYSMAN_APM','BIP','SYSMAN_OPSS','SYSMAN_RO') and owner='PUBLIC';


select 'drop synonym '|| OWNER||'.'||synonym_name || ' ;'  from dba_synonyms where table_owner in ('SYSMAN','SYSMAN_MDS','MGMT_VIEW','SYSMAN_BIP','SYSMAN_APM','BIP','SYSMAN_OPSS','SYSMAN_RO') and owner<>'PUBLIC';


drop user SYSMAN_MDS cascade;
drop user MGMT_VIEW cascade;
drop user SYSMAN_BIP cascade;
drop user SYSMAN_APM cascade;
drop user BIP cascade;
drop user SYSMAN_OPSS cascade;
drop user SYSMAN_RO cascade;
drop user SYSMAN cascade;


 drop tablespace MGMT_ECM_DEPOT_TS including contents and datafiles;

 drop tablespace MGMT_TABLESPACE including contents and datafiles;

 drop tablespace MGMT_AD4J_TS  including contents and datafiles;