Optimizer
The optimizer is an important part of the Db2 for i database engine because it makes the key decisions for good database performance. Its main objective is to find the most efficient access path to the Db2 for i data.
Query optimization is a trade-off between the time spent to select a query implementation and the time spent to run it. Query optimization must handle the following distinct user needs:
- Quick interactive response
- Efficient use of total-machine resources
In deciding how to access data, the optimizer does the following:
- Determines possible implementations
- Picks the optimal implementation for running of the SQL statement