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Examine the parallelism parameters for your instance:
What are true about the execution of the query?
A. It will execute in parallel only if the LINEITEM table has a dictionary DOP defined.
B. DOP for the statement is determined by the dictionary DOP of the accessed objects.
C. It is generated to execute in parallel.
D. It will execute in parallel only if the estimated execution time is 10 or more seconds.
E. DOP for the statement is calculated automatically.
F. It may execute serially.
Correct Answer: EF
Explanation/Reference:
E:
F (not C): It may execute serially. See note below.
Incorrect:
A, B: Dictionary DOP not used with PARALLEL (AUTO) hint.
D: The default value of parallel_min_time_threshold is 30 (not 10) seconds.
Note:
* parallel_min_percent
PARALLEL_MIN_PERCENT operates in conjunction with PARALLEL_MAX_SERVERS and PARALLEL_MIN_SERVERS. It lets you specify the minimum percentage of parallel execution processes (of the value of PARALLEL_MAX_SERVERS) required for parallel execution. Setting this parameter ensures that parallel operations will not execute sequentially unlessadequate resources are available. The default value of 0 means that no minimum percentage of processes has been set.
Consider the following settings:
PARALLEL_MIN_PERCENT = 50
PARALLEL_MIN_SERVERS = 5
PARALLEL_MAX_SERVERS = 10
If 8 of the 10 parallel execution processes are busy, only 2 processes are available. If you then request a query with a degree of parallelism of 8, the minimum 50% will not be met.
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