Using REVERSE with CLOB data in oracle 12c

Hi all,

I have a column with data type is NCLOB (the length > 4000). I need to use REVERSE for this column as the bellow code:

declare

     l_data varchar2(32767);

     l_data1 varchar2(32767);

begin

     for rc in (select <clob_field>  from ... where ...)

     loop

          l_data := dbms_lob.substr( rc.<clob_field>, 32767, 1 );

          select REVERSE(l_data) into l_data1 from dual;  --> ORA-01460: unimplemented or unreasonable conversion requested

          insert into test values(l_data1);

     end loop;

     commit;

end;

Is the size of clob problem for REVERSE? Does oracle have alternative methods with this situation?

Thanks,

Beck.