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>

SQL> select CONSTRAINT_NAME,CONSTRAINT_TYPE,DELETE_RULE from user_constraints where TABLE_NAME='CHILD_TABLE';

CONSTRAINT_NAME                C DELETE_RU
------------------------------ - ---------
FK_PARENT_TAB                  R CASCADE

  1  select r.CONSTRAINT_NAME,r.DELETE_RULE,p.table_name pk_table
  2  from user_constraints r,user_constraints p
  3* where r.TABLE_NAME='CHILD_TABLE' and r.constraint_type='R' and p.CONSTRAINT_NAME(+)=r.R_CONSTRAINT_NAME
SQL> /

CONSTRAINT_NAME                DELETE_RU PK_TABLE
------------------------------ --------- ------------------------------
FK_PARENT_TAB                  CASCADE   PARENT_TABLE

  1  select r.table_name,r.CONSTRAINT_NAME,r.DELETE_RULE,p.table_name pk_table
  2  from user_constraints r,user_constraints p
  3* where r.TABLE_NAME='CHILD_TABLE' and r.constraint_type='R' and p.CONSTRAINT_NAME(+)=r.R_CONSTRAINT_NAME
SQL> /

TABLE_NAME                     CONSTRAINT_NAME                DELETE_RU PK_TABLE
------------------------------ ------------------------------ --------- ------------------------------
CHILD_TABLE                    FK_PARENT_TAB                  CASCADE   PARENT_TABLE