let autotrace available for public

1.1 create plan_table table
SQL> conn / as sysdba
SQL> @?/rdbms/admin /utlxplan.sql
SQL> create public synonym plan_table for plan_table;
SQL> grant all on plan_table to public;

1.2 create plustrace role
SQL> @?/sqlplus/admin/plustrce.sql
SQL> grant plustrace to public;