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How SELECT affects remote database from which data is selected [message #366296]

Fri, 12 December 2008 12:42

lotusdeva
Messages: 201
Registered: March 2005

Senior Member

Hi,
A am having a discussion.
My opponent thinks that
statements like SELECT*FROM schema_name.table_name@remote_database_link
affects performance on remote database.
I disagree, but I could not find supporting materials.
Please help, it is important!

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Re: How SELECT affects remote database from which data is selected [message #366300 is a reply to message #366296]

Fri, 12 December 2008 12:52

Michel Cadot
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Registered: March 2007
Location: Saint-Maur, France, https...

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Quote:

Please help, it is important!

Why? It is just a discussion.

Of course, doing something is more expensive than doing nothing.

Regards
Michel

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Re: How SELECT affects remote database from which data is selected [message #366320 is a reply to message #366300]

Fri, 12 December 2008 15:49

lotusdeva
Messages: 201
Registered: March 2005

Senior Member

It is not just a discussion. It is a business decission issue.

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Re: How SELECT affects remote database from which data is selected [message #366322 is a reply to message #366320]

Fri, 12 December 2008 16:36

Mahesh Rajendran
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>>affects performance on remote database.
How much exactly? In what measure?
Restating Michel's words in another form ,
nothing is free.
In certain cases, even just a select statement may create redo (not directly. undo creates redo). Search this forum. There are numerous examples for this/delayed block cleanout.
Succinctly put (and shamelessly plagiarizing Michel),
doing something is expensive than doing nothing.

[Updated on: Fri, 12 December 2008 16:36]

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Re: How SELECT affects remote database from which data is selected [message #366325 is a reply to message #366322]

Fri, 12 December 2008 16:56

lotusdeva
Messages: 201
Registered: March 2005

Senior Member

Mahesh,

I select data from database/schema X from database/schema Y. To my understanding, no redo/undo or any other do can be generated on database Y.

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Re: How SELECT affects remote database from which data is selected [message #366328 is a reply to message #366325]

Fri, 12 December 2008 17:09

Mahesh Rajendran
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>>no redo/undo or any other do can be generated on database Y.

Did you care to search the forum?
When you issue a select(no matter from where), Oracle will generate a read consistent image of data from undo records and present it to you. This undo will generate redo.

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Re: How SELECT affects remote database from which data is selected [message #366329 is a reply to message #366325]

Fri, 12 December 2008 17:11

Mahesh Rajendran
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Location: oracleDocoVille

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http://www.orafaq.com/forum/m/163593/42800/?srch=delayed+block+cleanout#msg_163593

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Re: How SELECT affects remote database from which data is selected [message #366365 is a reply to message #366325]

Sat, 13 December 2008 01:31

Michel Cadot
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If you just want a short answer, yes it will affect performances on remote database.

Regards
Michel

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