I queried to see the list of all username in the database. However,
I see duplicate user accounts. How can I fix it? Below is the sample.

SQL> select username, created
2 from dba_users
3 order by 1;

USERNAME CREATED
------------------------------ ---------
DBSNMP 16-MAY-02
DBSNMP 16-MAY-02
OUTLN 16-MAY-02
OUTLN 16-MAY-02
SYS 16-MAY-02
SYS 16-MAY-02
SYSTEM 16-MAY-02
SYSTEM 16-MAY-02
TRACESVR 16-MAY-02
TRACESVR 16-MAY-02