query performance

Hi

Is there anyway to imporove performance of this EBS query?

 

 SELECT B.LOBS,
               B.SEGMENT2,
               &P_PERIOD PERIOD_NAME,
               TO_CHAR(TO_DATE(SUBSTR(&P_PERIOD, 5), 'RRRR'), 'YYYY') PERIOD_YEAR,
               'P' CTAG,
               'Y' TYP,
               -SUM(DECODE(SUBSTR(B.PERIOD_NAME, 1, 3), D.MONTHS, B.PTD, NULL))
  FROM (SELECT A.LOBS,
               A.SEGMENT2,
               A.PERIOD_NAME,
               A.PERIOD_YEAR,
               NVL(SUM(A.ACCOUNTED_DR), 0) - NVL(SUM(A.ACCOUNTED_CR), 0) PTD
          FROM (SELECT C.SEGMENT2,
                       DECODE((select MIN(cc.segment7)
                                from Xla_Ae_Lines l, gl_code_combinations cc
                               where l.code_combination_id =
                                     cc.code_combination_id
                                 and l.ae_header_id = xal.ae_header_id