As stated by Randolf Geist in his blog post oracle introduced a new model for predicting the execution time from the cost calculation starting from patch set 126.96.36.199 and this kick in after running the I/O calibration routine.Without I/O calibration the execution time will still be as usual COST*SINGLE-BLOCK read time.
Extract from Randolf Geist post Cost Is Time: Next Generation :
“The cost that has been calculated according to the System Statistics model – which is already a time estimate based on three different components – time for single-block and multi-block reads as well as the estimated CPU time is now converted into a data volume by simply multiplying the resulting cost with the default block size. Dividing this data volume by the throughput as indicated by the I/O calibration results (it looks like the value MAX_PMBPS is relevant) arrives at a new estimated execution time.”
So what about 12C ? Let’s run some test and observe :