I AM TRYING TO FETCH DATA FROM A TABLE THROUGH A CURSOR WHICH MIGHT CONTAIN MSISDN NUMBERS IN DUPLICATE. I HAVE TO FETCH THEM AND THEN PERFORM A SUM FUNCTION FOR THE 'MOU' COLUMN OF THOSE DUPLICATE MSISDN NUMBERS.
THIS CURSOR IS WORKING VERY SLOW. IT TAKES 5 MINUTES TO INSERT OR UPDATE ONLY 1000 RECORDS.
KINDLY HELP HOW TO SPEED UP THE EXECUTION TIME. OR SUGGEST IF THERE IS SOMETHING WRONG WITH THE LOGIC I AM EXECUTING..
THE CODE IS AS FOLLOWS:



CREATE PROCEDURE DCSDEV.UPDATE_USAGEDATADUMMY()
LANGUAGE SQL
P1: BEGIN

DECLARE lv_DUMMYVAR DOUBLE;
DECLARE lv_MSISDN_CURS VARCHAR(45);
DECLARE lv_DATE_CURS DATE;
DECLARE V INT DEFAULT 0;

DECLARE DUP_VOICE_RECS CURSOR WITH RETURN FOR (
SELECT MSISDN_NO, CALL_DATE FROM TEMP_VOICE_USAGE GROUP BY MSISDN_NO, CALL_DATE HAVING COUNT(MSISDN_NO) > 1) ;

OPEN DUP_VOICE_RECS;
FETCH_DUP_VOICE_RECS: LOOP
FETCH DUP_VOICE_RECS INTO lv_MSISDN_CURS, lv_DATE_CURS;
SELECT COUNT(MSISDN) INTO V FROM USAGE_DATA WHERE MSISDN = lv_MSISDN_CURS AND USAGE_DATE = lv_DATE_CURS;
SELECT SUM(DOUBLE(MOU)) INTO lv_DUMMYVAR FROM TEMP_VOICE_USAGE WHERE MSISDN_NO = lv_MSISDN_CURS;
IF V=0
THEN
INSERT INTO USAGE_DATA (MSISDN, USAGE_DATE, MOU) VALUES (lv_MSISDN_CURS, lv_DATE_CURS, lv_DUMMYVAR);
ELSE
UPDATE USAGE_DATA SET MOU = (MOU + lv_DUMMYVAR) WHERE MSISDN = lv_MSISDN_CURS;
END IF;
DELETE FROM TEMP_VOICE_USAGE WHERE MSISDN_NO = lv_MSISDN_CURS;
END LOOP;
CLOSE DUP_VOICE_RECS;

END P1
GO

You are using procedural processing, where you do something for each record in TEMP_VOICE_USAGE. The "something" is the execution of 2 SQL statements (1x INSERT or UPDATE and 1x DELETE). It is not very surprising that it performs poorly for you. Especially if you consider that the DELETE is a searched-delete and not a positioned-delete. (A positioned delete uses WHERE CURRENT OF <cursor>.)

You may want to use SQL in a set-oriented fashion. You may want to use the MERGE statement. Another option would be to have 1x INSERT for all new records, 1x UPDATE for all existing ones and then a single DELETE (no loops):
(modulo typing errors)