Speeding up query processing

Question

Hi,
I was wondering if anyone had any suggestions on how to improve the performance of this code? All table used are indexed. The calling routine for this procedure is set into a for loop. I am working on Oracle8i release 8.1.7.4.0.
Thanks,
Darren
CREATE OR REPLACE PACKAGE aa_mars
AS
     PROCEDURE get_mars_info;
END aa_mars;
CREATE OR REPLACE PACKAGE BODY aa_mars
AS
PROCEDURE get_mars_info
IS
     Variables
     TYPE MPANS is TABLE OF by_recon_mpans.mpan_core%TYPE;
     mpan MPANS;     
     lv_module_name VARCHAR2(30) := 'Populate MARS Alignment Info';
     lv_sqlerrm VARCHAR2(2000) := '';
     ln_sqlcode NUMBER := 0;
     lv_error_text VARCHAR2(2000) := '';
     vv_control           VARCHAR2(20);          
BEGIN
     --dbms_output.put_line ('Started :'||TO_CHAR(SYSDATE,'DD/MM/YY HH24:MI:SS'));
     SELECT a.mpan_core BULK COLLECT
     INTO mpan
     FROM      by_recon_mpans a
     WHERE      NOT EXISTS(SELECT 1
                         FROM aa_mars_info b
                         WHERE a.mpan_core = b.mpan_core)
     AND      SUBSTR(a.mpan_core,1,2) IN (13,18)
     AND      ROWNUM < 2000;
/********** MARS DETAILS ******************************/
     FORALL i in mpan.FIRST..mpan.LAST
          INSERT      INTO aa_mars_info
                    mpan_core
          ,           reg_id
          ,           reg_efd
          ,           reg_etd
          ,           meter_id
          SELECT DISTINCT r.ms_mpan_core mpan_core
          ,           r.register_channel_id reg_id
          ,           MIN(r.effective_from_date) reg_efd
          , MAX( DECODE( r.effective_to_date, TO_DATE('01-JAN-4000', 'DD-MON-YYYY'),TO_DATE('31-DEC-2999', 'DD-MON-YYYY'),r.effective_to_date)) reg_etd
          ,           m.short_meter_id mtr_id
          FROM      registers@link_to_mars r
          ,           meters@link_to_mars m
          WHERE      m.meter_id=r.mtr_meter_id
          AND      m.effective_from=r.mtr_effective_from
          AND      r.ms_mpan_core = mpan(i)
          AND      r.effective_to_date IN (SELECT MAX (r1.effective_to_date)
                                             FROM registers@link_to_mars r1
                                                  WHERE r.ms_mpan_core = r1.ms_mpan_core)
          AND      r.mtr_meter_id IN (SELECT e.mtr_meter_id
                                        FROM registers@link_to_mars e
                                        WHERE e.ms_mpan_core=r.ms_mpan_core
                                        AND e.effective_to_date=r.effective_to_date)
          GROUP BY r.ms_mpan_core
          ,           r.register_channel_id          
          , m.short_meter_id;
          COMMIT;
     EXCEPTION HANDLER
     EXCEPTION
     WHEN OTHERS THEN
     lv_sqlerrm := SQLERRM;
     ln_sqlcode := SQLCODE;
     Tracker_Error_Handler.write_error(v_module_name => lv_module_name
                                             ,v_error_code => ln_sqlcode
                                             ,v_error_message => lv_sqlerrm
                                             ,v_additional_text => lv_error_text
                                             ,v_error_type => Dctrack_Constants.c_error_fatal);
     dbms_output.put_line(lv_error_text);
     ROLLBACK;     
END get_mars_info;
END aa_mars;
/

Answer 1

We only have read access on the database over the link. A view can be read only. I know, I know, what you mean is you aren't allowed to put additional objects on the remote database. Still I suggest you ask: it's it their interest to make your query as efficient as possible too, because they are the ones serving you the data, so it's dragging their system down too.
... without me having to copy all the tables to a local area?Well, that's what you're effectively doing anyway at the moment.
Do you have any further suggestions, Yes, use the LIMIT caluse in the bulk collect.
--  decalration section
CURSORC c_mpans IS
SELECT a.mpan_core
FROM by_recon_mpans a
WHERE NOT EXISTS(SELECT 1
FROM aa_mars_info b
WHERE a.mpan_core = b.mpan_core)
AND SUBSTR(a.mpan_core,1,2) IN (13,18);
BEGIN
   OPEN c_mpans;
   LOOP
       FETCH c_mpans BULK COLLECT INTO mpan LIMIT 2000;
       EXIT WHEN mpan.count() = 0;
       FORALL i IN mpan.FIRST..mpan.LAST
   END LOOP;
END;
/At least then you only call the procedure once and execute the main query once.
Cheers, APC