High no. of physical reads of a query in statspack report

Question

we have a Oracle database 9.2.0.6 on solaris box....
SQL ordered by Reads for DB: ic  Instance: ic12  Snaps: 19 -20
-> End Disk Reads Threshold:      1000
                                                     CPU      Elapsd
Physical Reads  Executions  Reads per Exec %Total Time (s)  Time (s) Hash Value
      1,103,253           77       14,328.0   53.1  1641.98  11428.17 3825541888
Module: w3wp.exe
select  MRH_MRN,DECODE(MRH_SEX,'M','MALE','FEMALE') AS SEX, trim
((mrh_sur_name||' '||mrh_first_name||' '||mrh_middle_name)) as M
EMNAME, decode(nvl(mrh_fellow_status_yn,'333'),'Y','FCA','ACA')
AS ACA_FCA, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADDR_LINE_1,'A',
MRH_RES_ADDR_LINE_1) AS L_ADD1, DECODE(MRH_RESI_STATUS,'I',MRH_Pexplain plan
SQL> explain plan for select  MRH_MRN,DECODE(MRH_SEX,'M','MALE','FEMALE') AS SEX
, trim((mrh_sur_name||' '||mrh_first_name||' '||mrh_middle_name)) as MEMNAME, de
code(nvl(mrh_fellow_status_yn,'333'),'Y','FCA','ACA')AS ACA_FCA, DECODE(MRH_RESI
_STATUS,'I',MRH_PROF_ADDR_LINE_1,'A',
  2  MRH_RES_ADDR_LINE_1) AS L_ADD1, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADDR_LI
NE_2,'A',MRH_RES_ADDR_LINE_2) AS L_ADD2, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ADD
R_LINE_3,'A',MRH_RES_ADDR_LINE_3) ASL_ADD3, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_
ADDR_LINE_4,'A',
  3  MRH_RES_ADDR_LINE_4) AS L_ADD4, DECODE(MRH_RESI_STATUS,'I',a.city_name,'A',
C.CITY_NAME) AS L_CITY, DECODE(MRH_RESI_STATUS,'I',MRH_PROF_ZIP_POSTAL_CODE,'A',
MRH_RES_ZIP_POSTAL_CODE) AS L_PIN, DECODE(MRH_RESI_STATUS,'I',b.cou_name,'A',D.C
OU_NAME) as L_Country,
  4  DECODE(MRH_RESI_STATUS,'I','NOT APPLICABLE',MRH_PROF_ADDR_LINE_1)AS R_ADD1,
DECODE(MRH_RESI_STATUS,'I',' ',MRH_PROF_ADDR_LINE_2)AS R_ADD2, DECODE(MRH_RESI_
STATUS,'I',' ',MRH_PROF_ADDR_LINE_3)
  5  AS R_ADD3, DECODE(MRH_RESI_STATUS,'I',' ',MRH_PROF_ADDR_LINE_4)AS R_ADD4, D
ECODE(MRH_RESI_STATUS,'I',' ','A',A.CITY_NAME) AS R_CITY, DECODE(MRH_RESI_STATUS
,'I',' ','A',MRH_PROF_ZIP_POSTAL_CODE) AS R_PIN, DECODE(MRH_RESI_STATUS,'I',' ',
'A',B.COU_NAME) as
  6  R_Country, decode(nvl(mrh_mem_sub_status,'555'),'26','EXPIRED','') as sub_s
tatus, decode(nvl(mrh_mem_status,'777'),'1','ACTIVE','2','REMOVED') as mem_statu
s,mrh_resi_status, DECODE(MRH_COP_STATUS,'1',DECODE(MRH_COP_TYPE ,'13','FULLTIME
-COP','1',
  7  'FULLTIME-COP', '12','PARTTIME-COP','2','PARTTIME-COP'),'NOT HOLDING COP')
AS COP_STATUS, TO_CHAR(MRH_ENROL_DT,'RRRR') AS ASSO_YR,TO_CHAR(MRH_FELLOW_DT,'RR
RR') AS FELLOW_YR from om_mem_reg_head,om_city A,
  8  om_country B,om_city C,om_country D  where  mrh_doc_status=5  and mrh_prof_
city_code=A.City_code(+) and mrh_prof_cou_code=B.cou_code(+)  and mrh_res_city_c
ode=C.City_code(+) and mrh_res_cou_code=D.cou_code(+) and trim((mrh_sur_name||'
'||mrh_first_name||
  9  ''||mrh_middle_name)) like upper('%%')  ORDER BY trim((mrh_sur_name||' '||m
rh_first_name||' '||mrh_middle_name))
10  ;
Explained.
SQL> select * from table(dbms_xplan.displaY());
PLAN_TABLE_OUTPUT
| Id  | Operation              |  Name            | Rows  | Bytes |TempSpc| Cost
  |
|   0 | SELECT STATEMENT       |                  |  2870 |   762K|       |  202
PLAN_TABLE_OUTPUT
8 |
|   1 |  SORT ORDER BY         |                  |  2870 |   762K|  1592K|  202
8 |
|   2 |   NESTED LOOPS OUTER   |                  |  2870 |   762K|       |  190
2 |
|   3 |    NESTED LOOPS OUTER  |                  |  2870 |   714K|       |  190
2 |
PLAN_TABLE_OUTPUT
|   4 |     HASH JOIN OUTER    |                  |  2870 |   667K|       |  190
2 |
|   5 |      HASH JOIN OUTER   |                  |  2870 |   616K|       |  189
2 |
|   6 |       TABLE ACCESS FULL| OM_MEM_REG_HEAD  |  2870 |   566K|       |  188
2 |
|   7 |       TABLE ACCESS FULL| OM_COUNTRY       |   677 | 12186 |       |
4 |
PLAN_TABLE_OUTPUT
|   8 |      TABLE ACCESS FULL | OM_COUNTRY       |   677 | 12186 |       |
4 |
|   9 |     INDEX UNIQUE SCAN  | CITY_CODE_PK     |     1 |    17 |       |
  |
|  10 |    INDEX UNIQUE SCAN   | CITY_CODE_PK     |     1 |    17 |       |
  |
PLAN_TABLE_OUTPUT
Note: cpu costing is off, PLAN_TABLE' is old version
18 rows selected.
SQL>Please suggest me whjat cab done to overcome the same
Edited by: user00726 on Feb 3, 2009 5:03 AM

Answer 1

SQL> show arraysize
arraysize 15
SQL>should i set SDU parameter in tnsnames and listener.ora
for more info related to the same...pls do visit the below thread:
n/w perfromance related problem