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I/O Resource Calibration

Cost Is Time: Next Generation

It looks like Oracle has introduced with the Oracle 11.2.0.2 patch set a new "cost is time" model for the time estimate of the Cost-Based Optimizer (CBO).

In order to understand the implications let me summarize the evolution of the CBO in terms of cost / time estimate so far:

1. Oracle 7 and 8

The cost estimate generated by the Cost-Based Optimizer (CBO) has always been a time estimate, although expressed in a slightly obscure unit, which is number of single block reads.