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Which three tasks are performed by the parallel execution coordinator process?
A. Allocating parallel execution processes from the parallel execution server pool.
B. Determining the parallel execution method for each operation in the execution plan.
C. Managing the data flow between the producers and consumers during inter-operation parallelism.
D. Any serial processing that is part of the execution plan.
E. Determining the desired number of parallel execution processes
F. Managing the data flow between the producers and consumers during intra-operation parallelism.
Correct Answer: ABC
Explanation/Reference:
A: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 Database can create additional parallel execution servers for the operation. These parallel execution servers remain with the operation throughout execution. After the statement has been processed completely, the parallel execution servers return to the pool.
B:
*The parallel execution coordinator examines each operation in a SQL statement’s execution plan then determines the way in which the rows operated on by the operation must be divided or redistributed among the parallel execution servers.
*After the optimizer determines the execution plan of a statement, the parallel execution coordinator determines the parallel execution method for each operation in the plan.
Note:
*Oracle Database can process a parallel operation with fewer than the requested number of processes. If all parallel execution servers in the pool are occupied and the maximum number of parallel execution servers has been started, the parallel execution coordinator switches to serial processing.
Reference:Oracle Database VLDB and Partitioning Guide11g,How Parallel Execution Works
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