SQL & PL/SQL

In this query ,Lio is very high.Please suggest how to low down the LIO

SELECT DISTINCT ool.org_id, ool.header_id, ooh.order_number, ool.line_id,
ool.line_number, ool.shipment_number,
NVL (ool.option_number, -99) option_number, xcl.GROUP_ID,
xcl.attribute3, xcl.attribute4
FROM oe_order_headers ooh,
xxcn_comp_header xch,
xxcn_comp_lines xcl,
fnd_lookup_values_vl fvl,
oe_order_lines ool
WHERE 1 = 1
AND ooh.org_id = 1524
AND xch.src_ref_no = TO_CHAR (ooh.order_number)
AND xch.src_ref_id = ooh.header_id
AND xch.org_id = 1524
AND xcl.header_id = xch.header_id
AND ool.line_id = xcl.oe_line_id
AND ool.flow_status_code IN
('WWD_SHIPPED',
'FULFILLED',
'SHIPPED',
'CLOSED',
'RETURNED'
)
AND ool.org_id = 1524
AND ool.header_id = ooh.header_id
AND xch.org_id = 1524
AND fvl.lookup_type = 'EMR OIC SOURCE FOR OU'
AND fvl.tag = '1524'
AND fvl.description = xch.SOURCE
AND EXISTS (
SELECT 1
FROM oe_order_lines oe
WHERE oe.header_id = ool.header_id
AND oe.org_id = 1524
AND oe.line_number = ool.line_number
AND oe.ordered_item = ool.ordered_item
AND oe.shipment_number > ool.shipment_number
AND NVL (oe.option_number, -99) =
NVL (ool.option_number,
-99)
AND NOT EXISTS (
SELECT 1
FROM xxcn_comp_lines xcl2
WHERE xcl.GROUP_ID = xcl2.GROUP_ID
AND oe.line_id = oe_line_id))


call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.07 0.12 12 25 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 103.03 852.42 176206 4997766 0 12
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 103.10 852.55 176218 4997791 0 12