physical block reads vs physical reads

physical block reads vs physical reads

Post by Doug Cowle » Sun, 31 Dec 1899 09:00:00

It states in one of Oracle's own teaching manuals, that if
physical block reads is a lot higher than physical reads, that
it's an indication that Oracle is doing a lot of FTS.
I guess this is because for every read, lots of physical blocks are
in one swoop.  Is this accurate?

If so, what sort of factors are involved in this ratio - would it be
MULTIBLOCK_IO_COUNT (not sure of exact spelling) only? Or
are there other factors that can affect it?



1. Logical reads Vs. Physical Reads

I have been using the optimizer/statistics io with 6.5 trying to optimize a
few Procedures/Indexes.  As I try different indexes, index types, etc., the
optimizer/statistics io returns the amount of physical and logical reads.
As expected, I get different amounts with different types of indexes.  What
I am wondering is what are Logical reads vs. Physical reads?  I have
searched all of my books, buy no one seems to know what they mean.  Of the
2, which is the most important to lower for optimization?

Any help is appreciated,

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