Whats the problem with this query?

Question

Its doing huge sort operations and is throwing the following all the time.
ORA-1652: unable to extend temp segment by 256 in tablespace
Unable to figure out if I should be increasing the sort area size. I initially increased the TEMP space by 50% to 3 G and it still fails. Any recommendations ?
SELECT distinct b.*,
f.carrier_id
FROM po a
JOIN (SELECT c.asn_shipment_id,
c.po_cd,
c.po_ln,
c.ve_cd,
c.itm_cd,
d.shipped_date,
c.qty_shipped,
d.transport_id
FROM po_asn_line_interface c
JOIN po_asn_interface d
ON to_char (c.asn_shipment_id) = to_char (d.asn_shipment_id)
WHERE c.stat_desc = 'ASN header invalid.'
AND d.stat_desc = 'Single vendor error: 1User-Defined Exception'
AND EXISTS (SELECT 1
FROM po_asn_line_interface e
WHERE c.po_cd <> e.po_cd
AND to_char(c.asn_shipment_id) = to_char(e.asn_shipment_id))) b
ON to_char (a.po_cd) = to_char (b.po_cd)
JOIN po_ln f
ON a.po_cd = f.po_cd
AND f.ln# = b.po_ln
WHERE a.stat_cd = 'O'
AND NOT EXISTS (SELECT 1
FROM po_ln$actn_hst e
WHERE e.po_cd = b.po_cd
AND e.ln# = b.po_ln
AND po_actn_tp_cd in ('SVB', 'RCV'))

Answer 1

Hi,
The types of SQL statements that can cause database sorts to occur include the following:
* ORDER BY
* GROUP BY
* SELECT DISTINCT
* UNION
* INTERSECT
* MINUS
* ANALYZE
* CREATE INDEX
* Joins between tables on columns that are not indexed
Making sure that all foreign key columns are indexed will also help reduce sorting when tables are joined via primary and foreign key columns. See also if you can avoid use DISTINCT clause in your SQL statement.
Cheers