Change the current_schema to the actual table owner by connecting as some other user in sql*plus and try renaming the table:
SQL> alter session set current_schema=scott;
Session altered.
SQL> rename emp to emp_back;
rename emp to emp_back
*
ERROR at line 1:
ORA-03001: unimplemented feature
Now: Try running the following command to rename the same table being in the same session with current_schema=scott;
SQL> alter table emp rename to emp_back;
Table altered.
SQL>
