How to tune this SQL (takes long time to come up with results)

Question

Dear all,
I have sum SQL which takes long time ... can any one help me to tune this.... thank You
SELECT SUM (n_amount)
FROM (SELECT DECODE (v_payment_type,
'D', n_amount,
'C', -n_amount
) n_amount, v_vou_no
FROM vouch_det a, temp_global_temp b
WHERE a.v_vou_no = TO_CHAR (b.n_column2)
AND b.n_column1 = :b5
AND b.v_column1 IN (:b4, :b3)
AND v_desc IN (SELECT v_trans_source_code
FROM benefit_trans_source
WHERE v_income_tax_app = :b6)
AND v_lob_code = DECODE (:b1, :b2, v_lob_code, :b1)
UNION ALL
SELECT DECODE (v_payment_type,
'D', n_amount,
'C', -n_amount
* -1 AS n_amount,
v_vou_no
FROM vouch_details a, temp_global_temp b
WHERE a.v_vou_no = TO_CHAR (b.n_column2)
AND b.n_column1 = :b5
AND b.v_column1 IN (:b12, :b11, :b10, :b9, :b8, :b7)
AND v_desc IN (SELECT v_trans_source_code
FROM benefit_trans_source
WHERE income_tax_app = :b6)
AND v_lob_code = DECODE (:b1, :b2, v_lob_code, :b1));
Thank You.....

Answer 1

Thanks a lot,
i did change the SQL it works fine but slows down my main query.... actually my main query is calling a function which does the sum......
here is the query.....?
select A.* from (SELECT a.n_agent_no, a.v_agent_code, a.n_channel_no, v_iden_no, a.n_cust_ref_no, a.v_agent_type, a.v_company_code,
a.v_company_branch, a.v_it_no, bfn_get_agent_name(a.n_agent_no) agentname,
PKG_AGE__TAX.GET_TAX_AMT(:P_FROM_DATE,:P_TO_DATE,:P_LOB_CODE,A.N_AGENT_NO)  comm,
c.v_ird_region
FROM agent_master a, agent_lob b, agency_region c
WHERE a.n_agent_no = b.n_agent_no
AND a.v_agency_region = c.v_agency_region
AND :p_lob_code = DECODE(:p_lob_code,'ALL', 'ALL',b.v_line_of_business)
AND :p_channel_no = DECODE(:p_channel_no,1000, 1000,a.n_channel_no)
AND :p_agency_group = DECODE(:p_agency_group,'ALL', 'ALL',c.v_ird_region)
group by a.n_agent_no, a.v_agent_code, a.n_channel_no, v_iden_no, a.n_cust_ref_no, a.v_agent_type, a.v_company_code, a.v_company_branch, a.v_it_no, bfn_get_agent_name(a.n_agent_no) ,
BPG_AGENCY_GEN_ACL_TAX.BFN_GET_TAX_AMOUNT(:P_FROM_DATE,:P_TO_DATE,:P_LOB_CODE,A.N_AGENT_NO),
c.v_ird_region
ORDER BY c.v_ird_region, a.v_agent_code DESC)
A
WHERE (COMM < :P_VAL_IND OR      COMM >=:P_VAL_IND1);
Any idea to make this faster....
Thank You...