EMCA – ORA-01921: role name ‘MGMT_USER’ conflicts with another user

A)Manually Resolve
1)If you fail after invoking command
emca -config dbcontrol db -repos create see alert log file for more details. Also refer to another log file if it shows. Directly go to step 3)

2)However I see many errors like,
CONFIG: ORA-00955: name is already used by an existing object
CONFIG: ORA-01921: role name ‘MGMT_USER’ conflicts with another user or role name
and many severals errors.

3)Execute the following commands in SQL*plus and then execute emca command. I wish no more error will come. After several experiment I get this.

drop user sysman cascade;
drop public synonym SETEMVIEWUSERCONTEXT;
drop role MGMT_USER;
drop PUBLIC SYNONYM MGMT_TARGET_BLACKOUTS;
drop user MGMT_VIEW;

And then,

$ emca -deconfig dbcontrol db
$ emca -config dbcontrol db -repos create

B)Using RepManager:
If I drop the Repository using RepManager like following error will not come while creating repository.
$ORACLE_HOME/sysman/admin/emdrep/bin/RepManager -action drop

This will not remove the configuration files, but only the repository related objects from the database.

But you need to remember when RepManager is ran the database will be put in Quiescing mode.