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Oracle: what is Single-Block or Multiblock IO

So, I know this is really a basic question, but I'm struggling to find the answer on Google, Wiki or Oracle. (Each technical document that I see suggests that these topics are already understood)

I am reading an article about the intricacies of Oracle Optimizer and how Explain Plan determines the cheapest plan for an SQL query. Right now, I am in a section on various access methods (for example, Full Index Scan and Quick Full Index Scan ), and I continue to see links to Block and Multiblock .

I have seen these concepts before, but I only vaguely understand that this is due to the way the Oracle engine accesses data stored on blocks.

Questions

  • Can someone explain to me the difference between these two types of reading and why in certain situations it might be more beneficial to do the other?
  • What is the importance of scanning a full index using single-block reading and quickly scanning a full index using multi-block reading?
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Multiblock I/O , READ- . (11gR2 12c) -, . - 1 . - DB_FILE_MULTIBLOCK_READ_COUNT.

: 8kb. 8kb , . , / Singleblock, 1 8kb - ( , , - , ). , , , , , , 8 8 8 , - , , 1 . Oracle - 1 (128 8 ) READ 128 , , -.

DB_FILE_MULTIBLOCK_READ_COUNT - . Latter Oracle Database .

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