Explain plan - lower cost but higher response time in 11g compared to 10g

Question

Hello,
I have a strange scenario where 'm migrating a db from standalone Sun FS running 10g RDBMS to a 2-Node Sun/ASM 11g RAC env. The issue is with response time of queries -
In 11g Env:
SQL> select last_analyzed, num_rows from dba_tables where owner='MARKETHEALTH' and table_name='NCP_DETAIL_TAB';
LAST_ANALYZED NUM_ROWS
11-08-2012 18:21:12 3413956
Elapsed: 00:00:00.30
In 10g Env:
SQL> select last_analyzed, num_rows from dba_tables where owner='MARKETHEALTH' and table_name='NCP_DETAIL_TAB';
LAST_ANAL NUM_ROWS
07-NOV-12 3502160
Elapsed: 00:00:00.04If you look @ the response times, even a simple query on the dba_tables takes ~8 times. Any ideas what might be causing this? I have compared the XPlans and they are exactly the same, moreover, the cost is less in the 11g env compared to the 10g env, but still the response time is higher.
BTW - 'm running the queries directly on the server, so no network latency in play here.
Thanks in advance
aBBy.

Answer 1

*11g Env:*
PLAN_TABLE_OUTPUT
Plan hash value: 4147636274
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1104 | 376K| 394 (1)| 00:00:05 |
| 1 | SORT ORDER BY | | 1104 | 376K| 394 (1)| 00:00:05 |
| 2 | TABLE ACCESS BY INDEX ROWID| NCP_DETAIL_TAB | 1104 | 376K| 393 (1)| 00:00:05 |
|* 3 | INDEX RANGE SCAN | IDX_NCP_DET_TAB_US | 1136 | | 15 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
3 - access("UNIT_ID"='ten03.burien.wa.seattle.comcast.net')
15 rows selected.
*10g Env:*
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 4147636274
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1137 | 373K| 389 (1)| 00:00:05 |
| 1 | SORT ORDER BY | | 1137 | 373K| 389 (1)| 00:00:05 |
| 2 | TABLE ACCESS BY INDEX ROWID| NCP_DETAIL_TAB | 1137 | 373K| 388 (1)| 00:00:05 |
|* 3 | INDEX RANGE SCAN | IDX_NCP_DET_TAB_US | 1137 | | 15 (0)| 00:00:01 |
Predicate Information (identified by operation id):
3 - access("UNIT_ID"='ten03.burien.wa.seattle.comcast.net')
15 rows selected.
The query used is:
explain plan for
select
NCP_DETAIL_ID ,
NCP_ID ,
STATUS_ID ,
FIBER_NODE ,
NODE_DESC ,
GL ,
FTA_ID ,
OLD_BUS_ID ,
VIRTUAL_NODE_IND ,
SERVICE_DELIVERY_TYPE ,
HHP_AUDIT_QTY ,
COMMUNITY_SERVED ,
CMTS_CARD_ID ,
OPTICAL_TRANSMITTER ,
OPTICAL_RECEIVER ,
LASER_GROUP_ID ,
UNIT_ID ,
DS_SLOT ,
DOWNSTREAM_PORT_ID ,
DS_PORT_OR_MOD_RF_CHAN ,
DOWNSTREAM_FREQ ,
DOWNSTREAM_MODULATION ,
UPSTREAM_PORT_ID ,
UPSTREAM_PORT ,
UPSTREAM_FREQ ,
UPSTREAM_MODULATION ,
UPSTREAM_WIDTH ,
UPSTREAM_LOGICAL_PORT ,
UPSTREAM_PHYSICAL_PORT ,
NCP_DETAIL_COMMENTS ,
ROW_CHANGE_IND ,
STATUS_DATE ,
STATUS_USER ,
MODEM_COUNT ,
NODE_ID ,
NODE_FIELD_ID ,
CREATE_USER ,
CREATE_DT ,
LAST_CHANGE_USER ,
LAST_CHANGE_DT ,
UNIT_ID_IP ,
US_SLOT ,
MOD_RF_CHAN_ID ,
DOWNSTREAM_LOGICAL_PORT ,
STATE
from markethealth.NCP_DETAIL_TAB
WHERE UNIT_ID = :B1
ORDER BY UNIT_ID, DS_SLOT, DS_PORT_OR_MOD_RF_CHAN, FIBER_NODE
This is the query used for Query 1.
Stats differences are:
1. Rownum differes by apprx - 90K more rows in 10g env
2. RAC env has 4 additional columns (excluded in the select statement for analysis purposes).
3. Gather Stats was performed with estimate_percent = 20 in 10g and estimate_percent = 50 in 11g.