Steps to remove "DATABASE SYSTEM" target from OEM 12C
The issue is after removing all the targets from a host , database system targets still appears in the oem.
So We have to remove this manually using EMCLI command for deleting this database system targets
Login to oem database and use the below query to find the target
select target_name, target_type from sysman.mgmt_targets where target_type like '%test%';
TEST_RACNODE1 oracle_database
TEST_RACNODE1_sys oracle_dbsys
emcli delete_target -name="TEST_RACNODE1" -type="oracle_database"
emcli delete_target -name="TEST_RACNODE1_sys" -type="oracle_dbsys"
Now check again,
select target_name, target_type from sysman.mgmt_targets where target_type like '%test%';
no rows selected.
Hope this helps ...