Need some help understanding parallels [message #673701] |
Wed, 05 December 2018 04:42 |
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sureshonly@hotmail.com
Messages: 9 Registered: December 2018
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Junior Member |
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Hi Guys,
I need some help in understanding how parallels work in different situations.
I got table A, B with parallel 10 degrees each.
When I run the below DML how it works and how many processors the DB look for
Create Table C PARALLEL (DEGREE 10) AS
SELECT A.* FROM A
JOIN B ON (A.COL1=B.COL1)
My server got 50 processors.
Can someone tell me what will be the performance of the query and what parallels I can use to tune it.
Regards,
Suresh
--moderator edit: added [code] tags, please do so yourself in future
[Updated on: Sat, 08 December 2018 02:34] by Moderator Report message to a moderator
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Re: Need some help understanding parallels [message #673703 is a reply to message #673701] |
Wed, 05 December 2018 06:21 |
John Watson
Messages: 8951 Registered: January 2010 Location: Global Village
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Senior Member |
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Welcome to the forum. Please read the OraFAQ Forum Guide and How to use code tags and make your code easier to read
No-one can tell you what the performance will be. You will have to run the query, and time it. Immediately after running it, if you run this
select dfo_number,tq_id,server_type,process,num_rows,instance from v$pq_tqstat
order by instance,tq_id,process;
you will see how the parallelism worked.
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Re: Need some help understanding parallels [message #673755 is a reply to message #673740] |
Sat, 08 December 2018 02:37 |
John Watson
Messages: 8951 Registered: January 2010 Location: Global Village
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Senior Member |
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I have no idea what you should assume, because you have no provided enough information. You need to show the results of the query you are running and the execution plan. Only by considering these together can one get any idea of what is happening.
If you do decide to post this information, please remember to enclose your copy/pastes within [code] tags, so that they are readable.
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Re: Need some help understanding parallels [message #673756 is a reply to message #673740] |
Sat, 08 December 2018 08:33 |
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BlackSwan
Messages: 26766 Registered: January 2009 Location: SoCal
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Senior Member |
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sureshonly@hotmail.com wrote on Fri, 07 December 2018 03:55Shall I assume its only using 15 Parallels for my above query?
Regards
Suresh
You have seen for yourself that 10 Parallel is slower than single thread processing.
So explain why you propose increasing parallel to 15 will be faster than either 10 or 1.
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