XML Query Have High Disk Reads.

Question

Question regarding XML data. When I query the following sql statement, the performance is fast. In addition, the explain plan shows that this query is efficient and utliizing all the indexes. However, when I query the v$sql table, I see that this query has very high physical read. Any idea as to why this query has a high physical read?
SELECT lpcs.TEXT_LOAN_PCH_CONT_CNTNT_XML.extract('/').getClobVal() as TEXT_CNTNT_XML
FROM REFTDBR1.LOAN_PCH_CONT_CNTNT_SET lpcs
WHERE lpcs.ID_LOAN_PCH_CONT = '9c24ede6-2bf0-4a9c-8345-fa986ec7516c'
AND lpcs.ind_deltn = 'N'
AND lpcs.ind_curr = 'Y'
DISK_READS
73488233

Answer 1

We're on Oracle 11Rg1 RAC with ASM architecture on Liinux platform. Below is the explain plan
SQL> explain plan for SELECT lpcs.TEXT_LOAN_PCH_CONT_CNTNT_XML.extract('/').getClobVal() as TEXT_CNTNT_XML
FROM REFTDBR1.LOAN_PCH_CONT_CNTNT_SET lpcs
WHERE lpcs.ID_LOAN_PCH_CONT = :1
AND lpcs.ind_deltn = 'N'
AND lpcs.ind_curr = 'Y' ;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 3814252188
Id Operation Name Rows Bytes Cost (%CPU) Time
0 SELECT STATEMENT 1 128 5 (0) 00:00:01
1 TABLE ACCESS BY INDEX ROWID LOAN_PCH_CONT_CNTNT_SET 1 128 5 (0) 00:00:01
* 2 INDEX RANGE SCAN LOAN_PCH_CONT_CNTNT_SET_X2 1 3 (0) 00:00:01
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
2 - access("LPCS"."ID_LOAN_PCH_CONT"=:1 AND "LPCS"."IND_CURR"='Y' AND "LPCS"."IND_DELTN"='N')
14 rows selected
This query was executed 1623 times so I guess that could explain the high disk reads? Does this mean that this query is not being stored in the buffer cache since the disk reads are high?
DISK_READS 73488233
FETCHES 1623
EXECUTIONS 1623