Query Tuning

Hi All,
I need ur help to tune the following query

DELETE /*+ Full(GTT) */ RPM_FUTURE_RETAIL_GTT GTT
WHERE
 GTT.PRICE_EVENT_ID = :B1 AND GTT.FUTURE_RETAIL_ID IN (SELECT /*+ Full(RFRG1)
  */ FUTURE_RETAIL_ID FROM RPM_FUTURE_RETAIL_GTT RFRG1 WHERE
  RFRG1.PRICE_EVENT_ID = :B1 AND RFRG1.ACTION_DATE < TO_DATE(TO_CHAR(:B3 ,
  'YYYY.MM.DD HH24:MI:SS'),'YYYY.MM.DD HH24:MI:SS') AND
  TRUNC(RFRG1.ACTION_DATE) >= TO_DATE(TRUNC(:B2 )) UNION ALL SELECT
  ZERO_DATE.FUTURE_RETAIL_ID FROM (SELECT /*+ Full(RFRG2) */
  RFRG2.FUTURE_RETAIL_ID, RANK() OVER (PARTITION BY RFRG2.ITEM,