Table 9-3 details one way to calculate the CPU consumption change for multiple SQL statements. By creating the status column index, each of the queries will consume only three logical IOs per execution. Based on their number of executions during the 30-minute sample interval, the expected logical IOs are calculated. Since each logical IO consumes around 0.0093 ms, the expected total CPU consumption per tuned SQL statement is calculated. When combined, the tuned statements will now consume only 0.0231 second of CPU, compared to the initial 230.553 seconds.

While the improvement seems dramatic, only when users trigger multiple and serial executing SQL statements are they likely to feel any difference. Additionally, total sample interval Oracle CPU consumption is 1,257 seconds (Figure 9-27), so a decrease of around 230 seconds may not result in much of a utilization improvement. But let's do the math, create the index, and see what happens.

Subtracting the CPU consumption from the statements shown in Table 9-3 (230.553 seconds), and then adding back their tuned CPU consumption of 0.0231 second, the expected Oracle CPU consumption becomes 1,026.948 seconds (1257.478 -230.553 + 0.023). Placing the expected CPU consumption into the standard utilization formula, we see the expected utilization is about 14%.