Parallel query hinting boosts certain query performances on multi-processor systems via parallel processing. The SQL optimizer determines when this is beneficial. On single-processor systems, this hint has no effect.

Parallel processing can be managed by:

1.  Setting the auto parallel option system-wide.
   

2. Using the %PARALLEL keyword in the FROM clause of specific queries.
   

%PARALLEL is ignored when it applied to:

1. INSERT, UPDATE, and DELETE queries (Only SELECT queries benefit from this feature)
2. The queries involving process-specific functions or variables
3. A subquery correlated with an