Impact on cost estimates
Most of the parameters specified in the ANLPARM and ANLCNTL parameter sets have some impact on the internal formulas and costing algorithms used by SQL PA.
The following list reviews the impact that specific parameters have on cost estimates.
- CPUCOST
- Establishes the base for the monetary cost estimates of CPU time.
- DEGREES
- Enables the optimizer to consider parallel processing; impacting sequential prefetch, I/O wait.
- HPOOLRD
- Governs read time of physical I/O: are they found in expanded storage, or read from disk? Impacts elapsed times and I/O waits; also influences asynchronous writes back to pool after insert, update, or delete activity.
- TIMCOST
- Establishes the base for the monetary cost estimates of elapsed time.
- VERSION
- Selects which set of path lengths are used, with different instruction counts on some functions.
You can obtain many varied results by manipulating the SQL PA parameters. It is important to remember that SQL PA can reflect any existing or proposed configuration description in its parameter set.