Which three factors does the estimator depend on for overall cost estimation of a given execution plan?

Question

Options

• ACardinality
• BSort area size
• COPTIMIZER_FEATURE_ENABLE parameter
• DNOT NULL_FEATURE_ENABLE parameter
• ENOT NULL constraint on a unique key column
• FLibrary cache size
• GThe units of work such as disk input/output, CPU usage, and memory used in an operation

• A
  76% (28)
• B
  3% (1)
• D
  8% (3)
• E
  3% (1)
• F
  11% (4)

Explanation

C: OPTIMIZER_FEATURES_ENABLE acts as an umbrella parameter for enabling a series of optimizer features based on an Oracle release number. Note: The estimator determines the overall cost of a given execution plan. The estimator generates three different types of measures to achieve this goal: This measure represents a fraction of rows from a row set. The selectivity is tied to a query predicate, such as last_name='Smith', or a combination of predicates. This measure represents the number of rows in a row set. This measure represents units of work or resource used. The query optimizer uses disk I/O, CPU usage, and memory usage as units of work. If statistics are available, then the estimator uses them to compute the measures. The statistics improve the degree of accuracy of the measures.

No community discussion yet for this question.