SP2-0618: Cannot find the Session Identifier. Check PLUSTRACE role is enabled SP2-0611: Error enabl

SQL> set autotrace on;
SP2-0618: Cannot find the Session Identifier.  Check PLUSTRACE role is enabled
SP2-0611: Error enabling STATISTICS report

SQL> select * from dba_roles where role='PLUSTRACE';

no rows selected

SQL> @?/sqlplus/admin/plustrce.sql
SQL>
SQL> drop role plustrace;
drop role plustrace
          *
ERROR at line 1:
ORA-01919: role 'PLUSTRACE' does not exist


SQL> create role plustrace;

Role created.

SQL>
SQL> grant select on v_$sesstat to plustrace;

Grant succeeded.

SQL> grant select on v_$statname to plustrace;

Grant succeeded.

SQL> grant select on v_$mystat to plustrace;

Grant succeeded.

SQL> grant plustrace to dba with admin option;

Grant succeeded.

SQL>
SQL> set echo off

[oracle@rg-zentao ~]$ sqlplus  /nolog

SQL*Plus: Release 11.2.0.2.0 Production on Fri Aug 16 10:18:20 2013

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

SQL> conn  scott/oracle
Connected.
SQL> set autotrace on;
SQL>