SQL> create table t as select * from scott.emp;

Table created.

SQL>
SQL> alter table t add primary key (empno);

Table altered.

SQL>
SQL> alter table t add constraint CK check ( sal >= 0 );

Table altered.

SQL>
SQL> create or replace
  2  trigger t_TRG
  3  before insert on t
  4  for each row
  5  begin
  6    :new.sal := :new.sal * 10 ;
  7  end;
  8  /

Trigger created.

SQL>
SQL> create table new_t (
  2     EMPNO                                              NUMBER(4)
  3    ,ENAME                                              VARCHAR2(10)
  4    ,JOB                                                VARCHAR2(9)
  5    ,MGR                                                NUMBER(4)
  6    ,HIREDATE                                           DATE
  7    ,SAL                                                NUMBER(7,2)
  8    ,COMM                                               NUMBER(7,2)
  9    ,DEPTNO                                             varchar2(20)  -- CHANGED
 10  );

Table created.

SQL>
SQL> exec dbms_redefinition.can_redef_table(user, 'T');

PL/SQL procedure successfully completed.

SQL>
SQL> exec dbms_redefinition.start_redef_table(user, 'T', 'NEW_T', col_mapping=>'empno,ename,job,mgr,hiredate,sal,comm,to_char(deptno) deptno');

PL/SQL procedure successfully completed.

SQL>
SQL> exec dbms_redefinition.sync_interim_table(user, 'T', 'NEW_T');

PL/SQL procedure successfully completed.

SQL>
SQL> set serveroutput on
SQL> declare
  2    l_err pls_integer;
  3  begin
  4    dbms_redefinition.copy_table_dependents(
  5      uname               => user,
  6      orig_table          => 'T',
  7      int_table           => 'NEW_T',
  8      num_errors          => l_err
  9      );
 10
 11    dbms_output.put_line('errors=' || l_err);
 12  end;
 13  /
errors=0

PL/SQL procedure successfully completed.

SQL>
SQL> exec dbms_redefinition.finish_redef_table(user, 'T', 'NEW_T');

PL/SQL procedure successfully completed.

SQL> drop table new_t purge;

Table dropped.

SQL> select object_name, status
  2  from user_objects
  3  where created > sysdate - 1/24;

OBJECT_NAME                              STATUS
---------------------------------------- -------
T_TRG                                    INVALID
SYS_C0032571                             VALID
T                                        VALID

3 rows selected.

SQL> alter trigger t_trg compile;

Trigger altered.

SQL>