Different Performance for a view/table

Question

Hi,
I have a view called "Myview" which has a poor performance on one database (DBTEST) but with good performance on another database (DBDEV)
I checked the indexes on both and all of them were in place on both databases.
DBTEST and DBDEV both installed on the same Unix machine (They share the same resources).
Since both databases are configured similarly I'm wondering why querying Myview view takes two times more to return records?
How can I identify where the problem is? The "consistent gets" and "physical reads" parameters are about 2 times more in DBTEST when I query the view. I believe this is why I have poor performance in DBTEST.
Could someone give me an advice on what db parameters I should verify to identify the problem?
DBTEST> select status from Myview where id =100;
elapse time: 40 seconds
DBDEV> select status from Myview where id =100;
elapse time: 22 seconds
DBTEST> select count(*) from Myview;
5123 rows selected
DBDEV> select count(*) from Myview;
4022 rows selected
Thanks,
Amir

Answer 1

There are 13 tables plus one view underlying the Myview
The tables which are not listed, are lookup tables and contain equal number of rows on both DBs:
DBDEV
TableName No of Rows
user_role                          3023
project                          2059
project_year 647
doc_tab 3091
user                                              3155
org                         2639
region                              125
application 3353
DBDEV
TableName No of Rows
user_role                          6362
project                          5058
project_year                         1516
doc_tab 8659
user                                              6936
org                         6320
region                              176
application 7325
Since Myview is using UNION clause I picked part of the execution plan:
DBDEV:
11 rows selected.
Elapsed: 00:00:16.01
Execution Plan
SELECT STATEMENT Optimizer=CHOOSE (Cost=525 Card=3 Bytes=111)
VIEW OF 'Myview' (Cost=525 Card=3 Bytes=111)
SORT (UNIQUE) (Cost=560 Card=3 Bytes=1103)
UNION-ALL
HASH JOIN (ANTI) (Cost=138 Card=1 Bytes=369)
HASH JOIN (Cost=135 Card=1 Bytes=356)
NESTED LOOPS (Cost=132 Card=1 Bytes=348)
NESTED LOOPS (OUTER) (Cost=131 Card=1 Bytes=330)
NESTED LOOPS (OUTER) (Cost=130 Card=1 ytes=308)
NESTED LOOPS (OUTER) (Cost=129 Card=1 Bytes=295)
FILTER
NESTED LOOPS (OUTER)
HASH JOIN (Cost=128 Card=1 Bytes=175)
VIEW OF 'Myview_PROJ_ALL_YEAR'
(Cost=123 Card=15 Bytes=2295)
MERGE JOIN (Cost=123 Card=15 Bytes=1935)
SORT (JOIN) (Cost=119 Card=529 Bytes=61893)
HASH JOIN (Cost=107 Card=529 Bytes=61893)
VIEW OF 'Myview_PROJECT' (Cost=100 Card=529 Bytes=44436)
SORT (UNIQUE) (Cost=100 Card=529 Bytes=40998)
UNION-ALL
HASH JOIN (Cost=9 Card=51 Bytes=2703)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=15 Bytes=135)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=6 Card=51 Bytes=2244)
HASH JOIN (Cost=48 Card=129 Bytes=11610)
HASH JOIN (Cost=41 Card=127 Bytes=9779)
HASH JOIN (Cost=29 Card=94 Bytes=5922)
HASH JOIN (Cost=9 Card=51 Bytes=2703)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=15 Bytes=135)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=6 Card=51 Bytes=2244)
TABLE ACCESS (FULL) OF 'APPLICATION' (Cost=19 Card=3353 Bytes=33530)
INDEX (FAST FULL SCAN) OF 'UK_user_INVOLVE' (UNIQUE) (Cost=11 Card=4527 Bytes=63378)
TABLE ACCESS (FULL) OF 'user_role' (Cost=6 Card=3023 Bytes=39299)
HASH JOIN (Cost=12 Card=298 Bytes=22350)
HASH JOIN (Cost=9 Card=51 Bytes=2907)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=15 Bytes=135)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=6 Card=51 Bytes=2448)
TABLE ACCESS (FULL) OF 'region' (Cost=2 Card=69 Bytes=1242)
HASH JOIN (Cost=19 Card=51 Bytes=4335)
HASH JOIN (Cost=12 Card=51 Bytes=3366)
HASH JOIN (Cost=9 Card=51 Bytes=2907)
DBINT:
9 rows selected.
Elapsed: 00:00:34.03
Execution Plan
SELECT STATEMENT Optimizer=CHOOSE (Cost=941 Card=3 Bytes=111)
VIEW OF 'Myview' (Cost=941 Card=3 Bytes=111)
SORT (UNIQUE) (Cost=976 Card=3 Bytes=1106)
UNION-ALL
HASH JOIN (ANTI) (Cost=253 Card=1 Bytes=370)
NESTED LOOPS (OUTER) (Cost=250 Card=1 Bytes=357)
NESTED LOOPS (OUTER) (Cost=250 Card=1 Bytes=341)
NESTED LOOPS (OUTER) (Cost=249 Card=1 Bytes=318)
HASH JOIN (Cost=248 Card=1 Bytes=304)
NESTED LOOPS (Cost=245 Card=1 Bytes=296)
HASH JOIN (Cost=243 Card=2 Bytes=556)
FILTER
HASH JOIN (OUTER)
VIEW OF 'Myview_PROJ_ALL_YEAR' (Cost=229 Card=35 Bytes=5355)
MERGE JOIN (Cost=229 Card=35 Bytes=4550)
SORT (JOIN) (Cost=226 Card=1262 Bytes=148916)
HASH JOIN (Cost=198 Card=1262 Bytes=148916)
VIEW OF 'Myview_PROJECT' (Cost=183 Card=1262 Bytes=106008)
SORT (UNIQUE) (Cost=183 (Card=1262 Bytes=100528)
UNION-ALL
HASH JOIN (Cost=15 Card=126 Bytes=6678)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=28 Bytes=252)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=12 Card=126 Bytes=5544)
HASH JOIN (Cost=98 Card=454 Bytes=41314)
HASH JOIN (Cost=88 Card=448 Bytes=34496)
HASH JOIN (Cost=48 Card=206 Bytes=12978)
HASH JOIN (Cost=15 Card=126 Bytes=6678)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=28 Bytes=252)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=12 Card=126 Bytes=5544)
TABLE ACCESS (FULL) OF 'APPLICATION' (Cost=32 Card=7325 Bytes=73250)
INDEX (FAST FULL SCAN) OF 'UK_user_INVOLVE' (UNIQUE) (Cost=39 Card=15889
Bytes=222446)
TABLE ACCESS (FULL) OF 'user_role' (Cost=9 Card=6362 Bytes=89068)
HASH JOIN (Cost=18 Card=556 Bytes=41700)
TABLE ACCESS (FULL) OF 'region' (Cost=2 Card=88 Bytes=1584)
HASH JOIN (Cost=15 Card=126 Bytes=7182)
TABLE ACCESS (FULL) OF 'GRANT_PROGRAM' (Cost=2 Card=28 Bytes=252)
TABLE ACCESS (FULL) OF 'PROJECT' (Cost=12 Card=126 Bytes=6048)
HASH JOIN (Cost=28 Card=126 Bytes=10836)
HASH JOIN (Cost=18 Card=126 Bytes=8316)
You see alapse time for querying DBTEST is sometimes 2 times more than DBDEV. BTW, I checked all indexes for both database are in place.
Based on the information provided can you tell me what the problem is?
Thanks,