Integer 

Dynamic. Scope = ALTER SESSION. 

0 

0 to 100 

OPTIMIZER_PERCENT_PARALLEL specifies the amount of parallelism that the optimizer uses in its cost functions.

The default of 0 means that the optimizer chooses the best serial plan. A value of 100 means that the optimizer uses each object's degree of parallelism in computing the cost of a full table scan operation. Low values favor indexes, and high values favor table scans.

Cost-based optimization is always used for queries that reference an object with a nonzero degree of parallelism. For such queries, a RULE hint or optimizer mode or goal will be ignored.  

Note: Use of a FIRST_ROWS hint or of optimizer mode override a non-zero setting of OPTIMIZER_PERCENT_PARALLEL. 

See Also: Oracle8i Designing and Tuning for Performance for more information on setting this parameter.