CURSOR c IS  
 SELECT id FROM parent
  WHERE status = 'delete'
  ORDER BY id;

OPEN c
  LOOP
    FETCH c BULK COLLECT INTO rec_tab LIMIT 5000
    FOR i IN 1..rectab.COUNT
    LOOP 
       < delete child records here and eventually the parent record >
    END LOOP;
    EXIT WHEN C%NOTFOUND;   
  END LOOP;
CLOSE c;

CURSOR c IS  
 SELECT * FROM temp_t
  ORDER BY id;

EXECUTE IMMEDIATE 'DROP TABLE temp_T';
EXECUTE IMMEDIATE 'CREATE GLOBAL TEMPORARY TABLE temp_t 
                    AS SELECT id FROM parent
                        WHERE status = 'delete';

SELECT COUNT(*) 
  INTO rec_ctr
  FROM temp_t;

WHILE rec_ctr > 0
LOOP

  -- note that this does not loop in the cursor  
  -- it opens the cursor, gets 5000 recs and closes it
  -- 
  OPEN c
    FETCH c BULK COLLECT INTO rec_tab LIMIT 5000
    FOR i IN 1..rectab.COUNT
    LOOP 
       < delete child records here and eventually the parent record >
       DELETE FROM temp_t WHERE id = rectab(i)   
       cOMMIT;
    END LOOP;
  CLOSE c;

SELECT COUNT(*) 
  INTO rec_ctr
  FROM temp_t;

END LOOP;

-- FIRST ITERATION    
-- CURSOR c has 15M records retrieved from TEMP_T
   OPEN c
     FETCH 5000 in BULK
     DELETE THE 5000 fetched records from TEMP_T
   CLOSE;

-- 2nd ITERATIOn
-- CURSOR c has 15M-5000  records retrieved from TEMP_T
   OPEN c
     FETCH 5000 in BULK
     DELETE THE 5000 fetched records from TEMP_T
   CLOSE;

-- 3nd ITERATIOn
-- CURSOR c has (15M-5000)-5000 records retrieved from TEMP_T
   OPEN c
     FETCH 5000 in BULK
     DELETE THE 5000 fetched records from TEMP_T
   CLOSE;

.. and so on UNTIL there are no more records in TEMP_T.

DELETE child_table
WHERE  child_id IN (SELECT child_id
                    FROM   parent_table
                    WHERE  status = 'delete');
--
DELETE parent_table
WHERE  status = 'delete'

SQL> DECLARE
  2    CURSOR c IS
  3           SELECT *
  4           FROM   ft_trns_input
  5           ORDER BY trns_input_id DESC;
  6    TYPE r_tab_type IS TABLE OF c%ROWTYPE;
  7    r_tab r_tab_type;
  8  BEGIN
  9    OPEN c;
 10    FETCH c BULK COLLECT INTO r_tab LIMIT 5000;
 11    CLOSE c;
 12  END;
 13  /

PL/SQL procedure successfully completed

Executed in 1.328 seconds

SQL> 

DELETE child_table
WHERE parent_id IN (SELECT parent_id
                    FROM   parent_table
                    WHERE  status = 'delete');
--
DELETE parent_table
WHERE  status = 'delete'

DELETE FROM child_table_1 WHERE parent_id IN (SELECT parent_id FROM parent WHERE status = 'delete';

DELETE FROM child_table_2 WHERE parent_id IN (SELECT parent_id FROM parent WHERE status = 'delete';

...

DELETE FROM child_table_8 WHERE parent_id IN (SELECT parent_id FROM parent WHERE status = 'delete';

CURSOR c IS SELECT parent_id FROM parent WHERE status = 'delete';

-- then have

DELETE FROM child_table_1 WHERE parent_id IN (c_rec.parent_id);
DELETE FROM child_table_2 WHERE parent_id IN (c_rec.parent_id);
...
DELETE FROM child_table_8 WHERE parent_id IN (c_rec.parent_id);