Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> RE: Re: parallel index creation again:in which case, can we use p

RE: Re: parallel index creation again:in which case, can we use p

From: John Kanagaraj <john.kanagaraj_at_hds.com>
Date: Thu, 13 Feb 2003 09:34:42 -0800
Message-ID: <F001.0054C324.20030213093442@fatcity.com> 





Stephen/Chao-ping,
 


I will side with Tom on this. In a single CPU situation, you want to avoid
context switches by _reducing_ the number of processes in a single CPU box.
Depending on other stuff such as processor/L2 cache flushing, this can be
quite a significant overhead. So PQ on a a single CPU box is essentially a
bad idea. 
 


John Kanagaraj


Oracle Applications DBA


DBSoft Inc


(W): 408-970-7002



What would you see if you were allowed to look back at your life at the end
of your journey in this earth?






-----Original Message-----


Sent: Thursday, February 13, 2003 7:40 AM
To: Multiple recipients of list ORACLE-L




Steve,
 


I believe what you say, but it seems counter-intuitive.  
 


If you only have one cpu, and you start two jobs, then it follows that the
cpu needs to split itself to do the work.
 


So, what are we gaining?  The CPU can only go so fast and do so much work.
 


Tom Mercadante 


Oracle Certified Professional 



-----Original Message-----


Sent: Thursday, February 13, 2003 9:39 AM
To: Multiple recipients of list ORACLE-L





tom, 



if the process is IO bound (ie consumes little cpu) then you can achieve a
lot. 



thanks, 



steve 







        "Mercadante, Thomas F" <NDATFM_at_labor.state.ny.us> 
Sent by: root_at_fatcity.com 




02/12/2003 02:23 PM 


Please respond to ORACLE-L 



        
        To:        Multiple recipients of list ORACLE-L
<ORACLE-L_at_fatcity.com> 
        cc:         
        Subject:        RE: Re: parallel index creation again:in which case,


can we use p	





If you only have one CPU, then is parallel either not supported, or simply a
waste of time?



I actually thought it was not supported.  If you only have one CPU, what do
you expect to gain?



Tom Mercadante


Oracle Certified Professional




-----Original Message-----


Sent: Wednesday, February 12, 2003 12:54 PM
To: Multiple recipients of list ORACLE-L
p




My experience shows that a parallel degree of less than 4 is nearly always
slower than serial. 



I would recommend tring parallel degree of 4.



-----Original Message-----


Sent: Wednesday, February 12, 2003 10:59 AM
To: Multiple recipients of list ORACLE-L
parallel with single cpu env?




Michael Ivanov,

                                 Hi, Thanks for your reply.
                                 In fact, I builded the index several times


like, and the


result is persistent across difference test case:

                                 So, I think buffer is not the cause of the


parallel


execution slower. But I really do not get other parameter to tune:(

                                 
                





SQL> set term on timing on echo on feedback on
SQL> alter session set sort_area_size = 100000000;



Session altered.



Elapsed: 00:00:00.01


SQL> create index idx_serial on viewcount( SID_LIST) nologging parallel
(degree 2) tablespace pqind;



Index created.



Elapsed: 00:18:01.36


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.16


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging tablespace
pqind;



Index created.



Elapsed: 00:06:48.04


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.06


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging parallel
(degree 2) tablespace pqind;



Index created.



Elapsed: 00:14:51.92


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.13


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging;



Index created.



Elapsed: 00:06:26.23


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.06


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging parallel
(degree 2) tablespace pqind;




Index created.



Elapsed: 00:14:44.58


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.13


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging tablespace
pqind;



Index created.



Elapsed: 00:06:49.09


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.07


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging parallel
(degree 2) tablespace pqind;



Index created.



Elapsed: 00:14:46.79


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.14


SQL> 



SQL>  create index idx_serial on viewcount( SID_LIST) nologging tablespace
pqind;



Index created.



Elapsed: 00:06:44.51


SQL>  drop index idx_serial;



Index dropped.



Elapsed: 00:00:00.07








Regards


zhu chao


msn:chao_ping_at_163.com


www.happyit.net


www.cnoug.org(China Oracle User Group)






>Dear Chao.

>Did you try change order of index's creating- first noparallel, second with

parallel. I think you will look other results.


>

>> hi, dba friends:

>>                  some paper said, pqo should only be used in SMP

machines, while


others


>> say, We can also use pqo in uniprocessor machines in some case. I am

trying


>> to use parallel index creation in the following env:

>>

>> Dell 1650 with 3 scsi160 disks and 1 CPU and 2G memory.

>> Oracle 9.2

>> Table contains 22000000 records,1.2GB

>> Table tablespace contains 3 datafiles , 400M, 400M and 600M, on seperate

3


>> disks. Index tablespace contains 3 datafiles, 200M, 200M and 200M on

>> seperate 3 disks.

>>

>>

>> SQL> set term on timing on echo on feedback on

>> SQL> alter session set sort_area_size = 100000000;

>> Session altered.

>> Elapsed: 00:00:00.01

>> SQL> create index idx_serial on viewcount( SID_LIST) nologging parallel

>> (degree 2) tablespace pqind; Index created. 

>> Elapsed: 00:18:01.36

>> SQL>  drop index idx_serial;

>> Elapsed: 00:00:00.16

>> SQL>  create index idx_serial on viewcount( SID_LIST) nologging

tablespace


>> pqind; Elapsed: 00:06:48.04

>>                  This machine is exclusived used my me and It seems that

PQO is


rather


>> slower than single thread. So is it still possible to use PQO on single

>> processor machines? Please share your experience and idear.

>>                  Thanks.

>>

>> Wait event like:

>>

>> Top 5 Timed Events

>> ~~~~~~~~~~~~~~~~~~                                                     

>> Total Event                                               Waits    Time

(s)


>> Ela Time -------------------------------------------- ------------

>> ----------- -------- PX qref latch                                     

>> 48,371         415    40.94 PX Deq: Execute Reply




>>       176         340    33.54 PX Deq Credit: send blkd




>>       47,704         248    24.47 control file parallel write




>>             112           5      .48 PX Deq Credit: need buffer




>>              1,835           4      .38

>> ------------------------------------------------------------- ^LWait

Events


>> for DB: ORA9  Instance: ora9  Snaps: 19 -20

>> -> s  - second

>> -> cs - centisecond -     100th of a second

>> -> ms - millisecond -    1000th of a second

>>

>>

>-- 

>Best regards

>Michael Ivanov, TD "ERA"






-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: chao_ping
 INET: chao_ping_at_vip.163.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Toepke, Kevin M
 INET: ktoepke_at_trilegiant.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Mercadante, Thomas F
 INET: NDATFM_at_labor.state.ny.us

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).





-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: John Kanagaraj
  INET: john.kanagaraj_at_hds.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).


Received on Thu Feb 13 2003 - 11:34:42 CST












Original text of this message













  HOME |
  ASK QUESTION |
  ADD INFO |
  SEARCH |
  E-MAIL US