Summary information |
|
|---|---|
Default value |
1000 |
Range of values |
1 – 65534 |
Status |
Dynamic |
Display level |
Comprehensive |
Required role |
System administrator |
Configuration group |
Query Tuning |
cost of a cpu unit specifies the cost of a single CPU operation.
The cost of a serial plan in the optimizer is described by this formula:
Cost = PIO X estimated_pio + LIO X estimated_lio + 100 X estimated_cpu / CPU
Where the default values are:
estimated_pio = 25
estimated_lio = 2
estimated_cpu = 1000
If your Adaptive Server has sufficient memory, then all tables exist in memory, and a value of 0 for cost of a physical io is appropriate.
If your CPU is fast enough so the value for cost of a cpu unit is not a issue, use this formula to determine the cost of CPU, which combines 2 LIO and 25 PIO (the default values):
CPU X 100/configuration_value
The default value for configuration_value is 1000.
As you increase the value for cost of a cpu unit, this formula reduces the impact of CPU on cost.
