Multiblock read count

As everyone will be aware, this parameter controls how much data Oracle thinks it can retrieve from the disks in a single trip (during a table scan). The important part of this statement is the "how much Oracle thinks". It is relatively easy to manufacture a circumstance where Oracle thinks it can achieve a much higher read size than can actually be serviced by the operating system. Unfortunately, this discrepancy can have an impact on performance, since the cost optimizer evaluates costs based on what Oracle thinks, not what is actually achievable.....................................

-by Connor McDonald

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