Parallel hint causes a query to run slower?

I have an insert...select query where the select is a join between a table with one billion rows (although there is a where clause on an indexed column that restricts it to "only" 300 million), a table with 30 million rows, and a table with about 100,000 rows, where the result is about 20 rows. When I first ran it, it took about 2 hours. I added a Parallel hint, and explain plan showed that it was being used (and v$session showed that I had about 30 additional connections while it ran). but not it takes four hours.
Is there a reason parallel processing would cause a query to run slower?
insert /*+ append */ into employees_by_age_group
pay_plan
, age_range
, pay_level
, fy
, employee_count
select /*+ parallel */
       emp.pay_plan
     , to_char(d.min_age) || '-' || to_char(d.max_age) as age_range
     , emp.pay_level
     , pay.fy
     , count(pay.employee_id) as employee_count
from
select /*+ index(pay_info pay_info_index_on_site) */
         employee_id
       , extract(year from (dte_ppe_end + 92)) as fy
       , count(employee_id) as num_recs
from pay_info
where extract(month from dte_ppe_end) = 10
and   extract(day from dte_ppe_end) between 14 and 27
and   substr(pay_type, 1, 1) IN ('A', 'B', 'C')
and   site like 'Z%'
group by employee_id, extract(year from (dte_ppe_end + 92))
) pay
join
select employee_id
       , pay_plan
       , pay_grade
       , pay_step
       , file_date
from
    select /*+ index(employee_info employee_info_index_on_site) */
           employee_id
         , pay_level
         , file_date
         , max(file_date)
           over (partition by extract(year from (file_date + 61)))
           as last_file_date
    from employee_info
    where site like 'Z%'
where file_date = last_file_date
) emp
on (
     emp.employee_id = pay.employee_id
     and extract(year from emp.file_date) = pay.fy - 1
join (
       select employee_id
            , dob
       from (
              select employee_id
                   , date_birth
                   , row_number() over (partition by employee_id order by date_file desc) as r
              from employee_birthdates
              where site like 'Z%'
       where r = 1
     ) dob
on dob.employee_id = pay.employee_id
join
            select 20 as min_age, 24 as max_age from dual
union all select 25 as min_age, 29 as max_age from dual
union all select 30 as min_age, 34 as max_age from dual
union all select 35 as min_age, 39 as max_age from dual
union all select 40 as min_age, 44 as max_age from dual
union all select 45 as min_age, 49 as max_age from dual
union all select 50 as min_age, 54 as max_age from dual
union all select 55 as min_age, 59 as max_age from dual
union all select 60 as min_age, 64 as max_age from dual
union all select 65 as min_age, 69 as max_age from dual
union all select 70 as min_age, 74 as max_age from dual
union all select 75 as min_age, 79 as max_age from dual
union all select 80 as min_age, 84 as max_age from dual
union all select 85 as min_age, 89 as max_age from dual
union all select 90 as min_age, 94 as max_age from dual
union all select 95 as min_age, 99 as max_age from dual
) d
group by emp.pay_plan, d.min_age, d.max_age, emp.pay_level, pay.fy;

Paul - here are three different explain plans
First, the original one (without the parallel hint):
INSERT STATEMENT ALL_ROWS                                              Cost: 26,684,255 Bytes: 114 Cardinality: 1
35 LOAD AS SELECT EMPLOYEES_BY_AGE_GROUP
    34 HASH GROUP BY                                                    Cost: 26,684,255 Bytes: 114 Cardinality: 1
      33 NESTED LOOPS                                                   Cost: 26,684,254 Bytes: 114 Cardinality: 1
        14 HASH JOIN                                                    Cost: 26,684,222 Bytes: 108 Cardinality: 1
          9 MERGE JOIN                                                  Cost: 4,408,803 Bytes: 8,322 Cardinality: 146
            3 VIEW DONBOT_DBA.                                          Cost: 114,863 Bytes: 29,625,180 Cardinality: 987,506
              2 WINDOW SORT PUSHED RANK                                 Cost: 114,863 Bytes: 35,550,216 Cardinality: 987,506
                1 TABLE ACCESS FULL TABLE EMPLOYEE_BIRTHDATES           Cost: 108,983 Bytes: 35,550,216 Cardinality: 987,506
            8 SORT JOIN                                                 Cost: 4,293,940 Bytes: 3,645 Cardinality: 135
              7 VIEW DONBOT_DBA.                                        Cost: 4,293,939 Bytes: 3,645 Cardinality: 135
                6 SORT GROUP BY                                         Cost: 4,293,939 Bytes: 4,185 Cardinality: 135
                  5 TABLE ACCESS BY INDEX ROWID TABLE PAY_INFO          Cost: 4,293,938 Bytes: 4,185 Cardinality: 135
                    4 INDEX RANGE SCAN INDEX PAY_INFO_INDEX_ON_SITE     Cost: 487,124 Cardinality: 402,683,034
          13 VIEW DONBOT_DBA                                            Cost: 22,275,300 Bytes: 1,160,143,257 Cardinality: 22,747,907
            12 WINDOW SORT                                              Cost: 22,275,300 Bytes: 841,672,559 Cardinality: 22,747,907
              11 TABLE ACCESS BY INDEX ROWID TABLE EMPLOYEE_INFO        Cost: 22,137,046 Bytes: 841,672,559 Cardinality: 22,747,907
                10 INDEX RANGE SCAN INDEX EMPLOYEE_INFO_INDEX_ON_SITE   Cost: 50,419 Cardinality: 38,019,281
        32 VIEW DONBOT_DBA
          31 UNION-ALL
            15 FAST DUAL Cost: 2 Cardinality: 1
            16 FAST DUAL Cost: 2 Cardinality: 1
            17 FAST DUAL Cost: 2 Cardinality: 1
            18 FAST DUAL Cost: 2 Cardinality: 1
            19 FAST DUAL Cost: 2 Cardinality: 1
            20 FAST DUAL Cost: 2 Cardinality: 1
            21 FAST DUAL Cost: 2 Cardinality: 1
            22 FAST DUAL Cost: 2 Cardinality: 1
            23 FAST DUAL Cost: 2 Cardinality: 1
            24 FAST DUAL Cost: 2 Cardinality: 1
            25 FAST DUAL Cost: 2 Cardinality: 1
            26 FAST DUAL Cost: 2 Cardinality: 1
            27 FAST DUAL Cost: 2 Cardinality: 1
            28 FAST DUAL Cost: 2 Cardinality: 1
            29 FAST DUAL Cost: 2 Cardinality: 1
            30 FAST DUAL Cost: 2 Cardinality: 1          Next, one with the parallel hint:
INSERT STATEMENT ALL_ROWS                                                                              Cost: 26,507,111 Bytes: 114 Cardinality: 1
51 LOAD AS SELECT EMPLOYEES_BY_AGE_GROUP
    50 PX COORDINATOR
      49 PX SEND QC (RANDOM) PARALLEL_TO_SERIAL SYS.:TQ10005 :Q1005                                     Cost: 26,507,111 Bytes: 114 Cardinality: 1
        48 HASH GROUP BY PARALLEL_COMBINED_WITH_PARENT :Q1005                                           Cost: 26,507,111 Bytes: 114 Cardinality: 1
          47 PX RECEIVE PARALLEL_COMBINED_WITH_PARENT :Q1005                                            Cost: 26,507,111 Bytes: 114 Cardinality: 1
            46 PX SEND HASH PARALLEL_TO_PARALLEL SYS.:TQ10004 :Q1004                                    Cost: 26,507,111 Bytes: 114 Cardinality: 1
              45 HASH GROUP BY PARALLEL_COMBINED_WITH_PARENT :Q1004                                     Cost: 26,507,111 Bytes: 114 Cardinality: 1
                44 NESTED LOOPS PARALLEL_COMBINED_WITH_PARENT :Q1004                                    Cost: 26,507,111 Bytes: 114 Cardinality: 1
                  25 HASH JOIN PARALLEL_COMBINED_WITH_PARENT :Q1004                                     Cost: 26,507,109 Bytes: 108 Cardinality: 1
                    17 PX RECEIVE PARALLEL_COMBINED_WITH_PARENT :Q1004                                  Cost: 4,301,500 Bytes: 4,104 Cardinality: 72
                      16 PX SEND HASH PARALLEL_TO_PARALLEL SYS.:TQ10003 :Q1003                          Cost: 4,301,500 Bytes: 4,104 Cardinality: 72
                        15 HASH JOIN PARALLEL_COMBINED_WITH_PARENT :Q1003                               Cost: 4,301,500 Bytes: 4,104 Cardinality: 72
                          7 BUFFER SORT PARALLEL_COMBINED_WITH_CHILD :Q1003
                            6 PX RECEIVE PARALLEL_COMBINED_WITH_PARENT :Q1003                           Cost: 4,293,939 Bytes: 1,809 Cardinality: 67
                              5 PX SEND BROADCAST PARALLEL_FROM_SERIAL SYS.:TQ10000                     Cost: 4,293,939 Bytes: 1,809 Cardinality: 67
                                4 VIEW DONBOT_DBA.                                                      Cost: 4,293,939 Bytes: 1,809 Cardinality: 67
                                  3 SORT GROUP BY                                                       Cost: 4,293,939 Bytes: 2,077 Cardinality: 67
                                    2 TABLE ACCESS BY INDEX ROWID TABLE PAY_INFO                        Cost: 4,293,938 Bytes: 2,077 Cardinality: 67
                                      1 INDEX RANGE SCAN INDEX PAY_INFO_INDEX_ON_SITE                   Cost: 487,124 Cardinality: 199,756,151
                          14 VIEW PARALLEL_COMBINED_WITH_PARENT DONBOT_DBA. :Q1003                      Cost: 7,561 Bytes: 29,625,180 Cardinality: 987,506
                            13 WINDOW SORT PUSHED RANK PARALLEL_COMBINED_WITH_PARENT :Q1003             Cost: 7,561 Bytes: 35,550,216 Cardinality: 987,506
                              12 PX RECEIVE PARALLEL_COMBINED_WITH_PARENT :Q1003                        Cost: 7,561 Bytes: 35,550,216 Cardinality: 987,506
                                11 PX SEND HASH PARALLEL_TO_PARALLEL SYS.:TQ10002 :Q1002                Cost: 7,561 Bytes: 35,550,216 Cardinality: 987,506
                                  10 WINDOW CHILD PUSHED RANK PARALLEL_COMBINED_WITH_PARENT :Q1002      Cost: 7,561 Bytes: 35,550,216 Cardinality: 987,506
                                    9 PX BLOCK ITERATOR PARALLEL_COMBINED_WITH_CHILD :Q1002             Cost: 7,557 Bytes: 35,550,216 Cardinality: 987,506
                                      8 TABLE ACCESS FULL TABLE PARALLEL_COMBINED_WITH_PARENT EMPLOYEE_BIRTHDATES :Q1002     Cost: 7,557 Bytes: 35,550,216 Cardinality: 987,506
                    24 BUFFER SORT PARALLEL_COMBINED_WITH_CHILD :Q1004
                      23 PX RECEIVE PARALLEL_COMBINED_WITH_PARENT :Q1004                                Cost: 22,205,605 Bytes: 575,504,145 Cardinality: 11,284,395
                        22 PX SEND HASH PARALLEL_FROM_SERIAL SYS.:TQ10001                               Cost: 22,205,605 Bytes: 575,504,145 Cardinality: 11,284,395
                          21 VIEW DONBOT_DBA.                                                           Cost: 22,205,605 Bytes: 575,504,145 Cardinality: 11,284,395
                            20 WINDOW SORT                                                              Cost: 22,205,605 Bytes: 417,522,615 Cardinality: 11,284,395
                              19 TABLE ACCESS BY INDEX ROWID TABLE EMPLOYEE_INFO                        Cost: 22,137,046 Bytes: 417,522,615 Cardinality: 11,284,395
                                18 INDEX RANGE SCAN INDEX EMPLOYEE_INFO_INDEX_ON_SITE                   Cost: 50,419 Cardinality: 18,859,958
                  43 VIEW PARALLEL_COMBINED_WITH_PARENT DONBOT_DBA. :Q1004                              Cost: 32 Bytes: 6 Cardinality: 1
                    42 UNION-ALL PARALLEL_COMBINED_WITH_PARENT :Q1004
                      26 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      27 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      28 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      29 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      30 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      31 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      32 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      33 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      34 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      35 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      36 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      37 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      38 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      39 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      40 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1
                      41 FAST DUAL PARALLEL_COMBINED_WITH_PARENT :Q1004         Cost: 2 Cardinality: 1                  Finally, one without the parallel hint, and without the index hint on PAY_TABLE:
INSERT STATEMENT ALL_ROWS                                              Cost: 23,348,654 Bytes: 114 Cardinality: 1
34 LOAD AS SELECT ARMYMP.EMPLOYEES_BY_AGE
    33 HASH GROUP BY                                                    Cost: 23,348,654 Bytes: 114 Cardinality: 1
      32 NESTED LOOPS                                                   Cost: 23,348,653 Bytes: 114 Cardinality: 1
        13 HASH JOIN                                                    Cost: 23,348,621 Bytes: 108 Cardinality: 1
          8 MERGE JOIN                                                  Cost: 1,073,202 Bytes: 8,322 Cardinality: 146
            3 VIEW DONBOT_DBA.                                          Cost: 114,863 Bytes: 29,625,180 Cardinality: 987,506
              2 WINDOW SORT PUSHED RANK                                 Cost: 114,863 Bytes: 35,550,216 Cardinality: 987,506
                1 TABLE ACCESS FULL TABLE EMPLOYEE_BIRTHDATES           Cost: 108,983 Bytes: 35,550,216 Cardinality: 987,506
            7 SORT JOIN                                                 Cost: 958,339 Bytes: 3,645 Cardinality: 135
              6 VIEW DONBOT_DBA.                                        Cost: 958,338 Bytes: 3,645 Cardinality: 135
                5 SORT GROUP BY                                         Cost: 958,338 Bytes: 4,185 Cardinality: 135
                  4 TABLE ACCESS FULL TABLE PAY_INFO                    Cost: 958,337 Bytes: 4,185 Cardinality: 135
          12 VIEW DONBOT_DBA.                                           Cost: 22,275,300 Bytes: 1,160,143,257 Cardinality: 22,747,907
            11 WINDOW SORT                                              Cost: 22,275,300 Bytes: 841,672,559 Cardinality: 22,747,907
              10 TABLE ACCESS BY INDEX ROWID TABLE EMPLOYEE_INFO        Cost: 22,137,046 Bytes: 841,672,559 Cardinality: 22,747,907
                9 INDEX RANGE SCAN INDEX EMPLOYEE_INFO_UIC              Cost: 50,419 Cardinality: 38,019,281
        31 VIEW DONBOT_DBA.                                             Cost: 32 Bytes: 6 Cardinality: 1
          30 UNION-ALL
            14 FAST DUAL Cost: 2 Cardinality: 1
            15 FAST DUAL Cost: 2 Cardinality: 1
            16 FAST DUAL Cost: 2 Cardinality: 1
            17 FAST DUAL Cost: 2 Cardinality: 1
            18 FAST DUAL Cost: 2 Cardinality: 1
            19 FAST DUAL Cost: 2 Cardinality: 1
            20 FAST DUAL Cost: 2 Cardinality: 1
            21 FAST DUAL Cost: 2 Cardinality: 1
            22 FAST DUAL Cost: 2 Cardinality: 1
            23 FAST DUAL Cost: 2 Cardinality: 1
            24 FAST DUAL Cost: 2 Cardinality: 1
            25 FAST DUAL Cost: 2 Cardinality: 1
            26 FAST DUAL Cost: 2 Cardinality: 1
            27 FAST DUAL Cost: 2 Cardinality: 1
            28 FAST DUAL Cost: 2 Cardinality: 1
            29 FAST DUAL Cost: 2 Cardinality: 1        I am surprised the cost without the index is less than the cost with it, considering that it is replacing a Table Access By Index Rowid with a Table Access Full on a table with 1 billion (1000 million) records.
Igor - two questions:
One - I cannot find "Materialize" in the hints in the SQL Reference anywhere. What does it do?
Two - does replacing subqueries with With clauses make that much of a difference?

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MacBook Pro 17 inch mid 2010, OSX 10.9.4, 2.53GHz Intel Core1.5, 4 GB
Can my Itunes library (it's large) cause my MacBook to run slow? Constantly getting the beachball. Have taken it to the Apple store and have dumped the system totally off the computer and reinstalled only the OS and Itunes again. Beyond slow. Takes at least 10 minutes to boot up if I turn it off.

If this started happening without your having made any changes and without a warning of low disk space, then it's likely that the startup drive, or some other hardware component, is failing. Back up all data immediately, then run Apple Diagnostics or the Apple Hardware Test.
Even if the test is negative, you should make a "Genius" appointment at an Apple Store to have the machine tested more thoroughly.

Parallel Hint !!

Hello Gurus
I m using prallel hint ...i belive the syntax of parallel hint is something like this
/*+ Parallel(tablename, degree) */But when i try with just degree without tablename, it works absolutely fine .... So my question is can i use parallel hint without tablename jus by mentioning degree
..like this
/*+    parallel(32) */My concern is, the query is has been deployed to production without the tablename being mentioned in parallel hint....so how serious is this ?? BUt when i run the query in dev without table name mentioning in parallel hint in Development area its running fine ...
So do u guys hav any suggestions!!
Thanks !!
Edited by: user642297 on May 26, 2010 11:13 AM

user642297 wrote:
I'm surprised it works without tablename (or alias for that tablename).
Yes it did work ...it did not through me any error!!
Hints that don't work because the syntax is not correct are just comments, they do not generate any errors.
SQL> select count(*) from
2 (select o.owner, count(*) from all_objects o,
3    (select level from dual connect by level <= 5)
4     group by o.owner);
COUNT(*)
       176
Elapsed: 00:01:07.01
SQL> edi
Wrote file afiedt.sql
1 select /*+ go_faster */ count(*) from
2 (select o.owner, count(*) from all_objects o,
3    (select level from dual connect by level <= 5)
4*    group by o.owner)
SQL> /
COUNT(*)
       176
Elapsed: 00:01:12.57

Macbook pro 2008 running slow

Im sorry if im reposting something somebody else has already poasted but I couldnt find this topic in the forum.
I have a 15" Macbook Pro bought December 2008 is my memory serves me correct
The specifics are
Model Name: MacBook Pro
Model Identifier: MacBookPro5,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.53 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 6 MB
Memory: 4 GB
Bus Speed: 1.07 GHz
I have about 129GB free, what I dont understand why it runs so slowly. I've run Disk Utilities and no errors or problems show up and frequently run CleanMyMac. I have recently installed Adobe CS5 but with 4GB RAM but I dont see why this would cause the computer to run slower as I should have enough ram. Can I upgrade to 6GB? Is there any other reason to why my computer would be running so slow? Applications often crash, or it can take me up to 5 min just closing an application down.
Thanks for the help!

I have the same era MBP and recently had to change to a new hard drive. I upgraded to a faster 7200 rpm drive and have no regrets. FYI, you don't have to buy a drive from them, but OtherWorld Computing does hace very helpful HD install videos (http://eshop.macsales.com/installvideos/macbookpro15_unibodyhd/) and also a handy $30 gizmo, the "USB 2 Universal Drive Adapter" that allows you to setup your new HD before installing into the MBP. Of course, if you already have a fast external FW drive you might not need it, but it worked like a charm. Also, the actual HD install in a unibody MBP literally only takes a couple of minutes.

Is using Parallel Hint /*+PARALLEL */ good or bad?

Hi,
I am facing problem in using /*+ PARALLEL */ hint in SQL Query its taken long time to execute.
Is using PARALLEL Hint degrades performance?
The Table FCT_TABLE is having PARALLEL ( DEGREE DEFAULT INSTANCES DEFAULT ) clause.
We are using parallel hint as SELECT /*+ PARALLEL(FCT_TABLE 2)
Any help will be needful for me.
Thanks and Regards

user598986 wrote:
We have noticed the following from the Server:
1.The Disk I/O is showing 0 always during the time of Execution of the Query.
2.The I/O Adapter is showing 700%.What is the o/s and version? Do you use any virtualisation? What storage system do you use? What RAID levels, if any? And how did you monitor these results?
Note that the physical I/O layer is not part of the database layer. From the database layer you typically address I/O issues with
- logical design (e.g. normalise data so that there's a single copy of the data to maintain and thus less I/O)
- physical design (e.g. use partitioning, IOTs, clusters, indexes and so on to facilitate less I/O to process data)
- parallelise (use multiple processes to perform large I/O scans to address some of the inherited latency issues when doing I/O)
- reduce I/O (e.g. by truncating a table or partition instead of deleting it, using CTAS, design s/w that only needs to make a single pass through a data set, etc)
From the database app level you have no control over where the data is stored, how it is stored and cached. So, as PL/SQL or app developer, your primary concern should be the amount of I/O your data model and app needs - as that is something you can and do control. And not worry about the physical implementation of the I/O layer. As that should be the concern of the sys admin and DBA of that platform.

Avoiding Parallel hints on a view

Hi All,
I am trying to avoid using Hints on a view.
Database: 11gr2.
Scenario:
I created a view
CREATE OR REPLACE VIEW customer_count_vw
AS SELECT /*+ NO_PARALLEL(T) */ COUNT(1) FROM customer;
When I see the explain plan it is going for a FULL TABLE Scan.
But When I use a hint on top of the view like
SELECT /*+ PARALLEL(A,12) */ * FROM customer_count_vw;
The explain plan is using the PARALLEL Hint.
Is there any way we can avoid this hint being applied on this view.
The reason why we want this scenario is , we are going to expose the view to the external people and if they force PARALLEL on the view, it will give a lot of problem for us in the PRODUCTION environment.
Appreciate your response.
THANKS,
MK.

>
we are going to expose the view to the external people and if they force PARALLEL on the view, it will give a lot of problem for us in the PRODUCTION environment.
>
You can't keep a query writer from using a PARALLEL hint in a query. But you can add a LOGON trigger that disables PARALLEL execution for the user sessions that you don't want to perform parallel ops. If you do that then PARALLEL will not be used for any other queries that session uses.

Power book runs slow and locks up

My powerbook G4 runs slow and then locks up and I have to force quit. A window pops up and say something to the effect that:
" a script is runing in this movie causing Macromedia Flash to run slow. If I dont turn it off it will get worst."
I am not runing a movie (?) nor a script that I know of. What can I do?

Welcome to the Apple discussions.
One place to start is to load the activity monitor, on your hard disk in applications/utilities, look at active tasks, and see what's running.

Parallel hint causes a query to run slower?

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