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Which four statements are correct about communication between parallel execution process?
A. The number of logical pathways between parallel execution producers and consumers depends on the degree parallelism.
B. The shared pool can be used for parallel execution messages buffers.
C. The large pool can be used for parallel execution messages buffers.
D. The buffer cache can be used for parallel execution message buffers.
E. Communication between parallel execution processes is never required if a query uses full partition-wise joins.
F. Each parallel execution process has an additional connection to the parallel execution coordinator.
Correct Answer: ABEF
Explanation/Reference:
A:Note that the degree of parallelism applies directly only to intra-operation parallelism. If inter-operation parallelism is possible, the total number of parallel execution servers for a statement can be twice the specified degree of parallelism. No more than two sets of parallel execution servers can run simultaneously. Each set of parallel execution servers may process multiple operations. Only two sets of parallel execution servers need to be active to guarantee optimal inter-operation parallelism.
B:By default, Oracle allocates parallel execution buffers from the shared pool.
F:When executing a parallel operation, the parallel execution coordinator obtains parallel execution servers from the pool and assigns them to the operation. If necessary, Oracle can create additional parallel execution servers for the operation. These parallel execution servers remain with the operation throughout job execution, then become available for other operations. After the statement has been processed completely, the parallel execution servers return to the pool.
Reference: OracleDatabase Data Warehousing Guide,Using Parallel Execution
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