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select statement

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vivek_k47
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select statement

Postby vivek_k47 » Wed Nov 07, 2012 10:30 am

Hi,
Can u please explain how the Select statement works in Oracle(how is it processed)
Also How does the server process know whether the data required is in the buffer cache or not?Which process keeps track of the data present in the DBBC?
Thanks.
Vivek

Tim...
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Re: select statement

Postby Tim... » Wed Nov 07, 2012 11:54 am

Hi.

That's not the sort of question you can answer with a couple of paragraphs in a forum. You probably need to start by reading this section of the concepts manual.

http://docs.oracle.com/cd/E11882_01/ser ... .htm#i8709

Regarding the buffer cache, there are basically two options here:

- Direct Path Reads: Some operations bypass the buffer cache completely and read the information directly into the UGA.
- Everything else: An attempt is made to read the block from the cache. If it's not present, it is read from disk into the cache.

Cheers

Tim...
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