Thanks for the question, Guduru.
Asked: October 05, 2018 - 5:56 am UTC
Last updated: October 06, 2018 - 6:25 am UTC
Version: 11.2.0.4
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Hi Tom,
I would like to know that, how Oracle internally manages when end user try to extract the data which is more than SGA, for Example if our SGA is 7 GB and user query is about 20 GB data, how it will internally manages, as far as I know, server process will fetch the data from the Data files and keep it in the buffer and returns the output to the user.
- SGA only will keep the sql id and hashvalue and not any data block. Is that right ?
I request you, could you please explain the complete scenario when the data extraction is more than SGA.
Many thanks in advance.,
Regards,
Balaji Gudru
and Connor said...
In simple terms, its similar to a LRU (Least Recently Used) algorithm...as the cache fills, we throw away the old stuff to make way for the new.
But if you want to see a very cool explanation along with animations on how it *really* works, check out Julian Dyke's presentation
http://www.juliandyke.com/Presentations/LogicalIO.ppt and run it in slideshow mode to see the animations. You wont be disappointed.