SQL> desc parent_table;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ID                                        NOT NULL NUMBER(38)
 N                                                  VARCHAR2(10)

SQL> desc child_table;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ID                                                 NUMBER(38)
 ID_P                                               NUMBER(38)
 C                                                  VARCHAR2(10)

SQL> create or replace TRIGGER B_PARENT_DELETE_FLAG
  2  BEFORE DELETE ON PARENT_TABLE
  3  BEGIN
  4   flag_on_delete_parent.flag:=true;
  5  END;
  6  /

Trigger created.


SQL> create or replace TRIGGER A_PARENT_DELETE_FLAG
  2  AFTER DELETE ON PARENT_TABLE
  3  BEGIN
  4   flag_on_delete_parent.flag:=false;
  5  END;
  6  /

Trigger created.
SQL> create or replace TRIGGER BACK_DELETE_CHILD
  2  BEFORE DELETE ON child_table
  3  FOR EACH ROW
  4  BEGIN
  5  if flag_on_delete_parent.flag then
  6   --insert into TABLE2BC ...
  7   dbms_output.put_line('Delete cascade child_table '||:old.id);
  8  end if;
  9  END;
 10  /

Trigger created.

SQL> select * from child_table;

        ID       ID_P C
---------- ---------- ----------
        10          1 Doc1
        20          1 Doc2
        30          1 Doc3

SQL> select * from PARENT_TABLE;

        ID N
---------- ----------
         1 Javl

SQL> delete child_table where id=20;

1 row deleted.

SQL> delete parent_table;
Delete cascade child_table 10
Delete cascade child_table 30

1 row deleted.

SQL>