SQL> select count(*) from emp;

  COUNT(*)
----------
        14

SQL> create or replace procedure truncate_table
  2  (TName in varchar2)
  3  authid current_user
  4  as
  5  str varchar2(300);
  6  begin
  7  str:='Truncate table '||TName;
  8  execute immediate str;
  9  end;
 10  /

Procedure created.

SQL> exec truncate_table('EMP');

PL/SQL procedure successfully completed.

SQL> select count(*) from emp;

  COUNT(*)
----------
         0