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Which two statements about In-Memory Parallel Execution are true?
A. It can be configured using the Database Resource Manager.
B. It increases the number of duplicate block images in the global buffer cache.
C. It requires setting PARALLEL_DEGREE_POLICY to LIMITED.
D. Objects selected for In-Memory Parallel Execution have blocks mapped to specific RAC instances.
E. It requires setting PARALLEL_DEGREE_POLICY to AUTO
F. Objects selected for In-Memory Parallel Execution must be partitioned tables or indexes.
Correct Answer: DE
Explanation/Reference:
D, E:In-Memory Parallel Execution
When the parameter PARALLEL_DEGREE_POLICY is set to AUTO, Oracle Database decides if an object that is accessed using parallel execution would benefit from being cached in the SGA (also called the buffer cache). The decision to cache an object is based on a well-defined set of heuristics including the size of the object and frequency on which it is accessed. In an Oracle RAC environment, Oracle Database maps pieces of the object into each of the buffer caches on the active instances. By creating this mapping, Oracle Database automatically knows which buffer cache to access to find different parts or pieces of the object. Using this information, Oracle Database prevents multiple instances from reading the same information from disk over and over again, thus maximizing the amount of memory that can cache objects. If the size of the object is larger than the size of the buffer cache (single instance) or the size of the buffer cache multiplied by the number of active instances in an Oracle RAC cluster, then the object is read using directpath reads.
E:PARALLEL_DEGREE_POLICY specifies whether or not automatic degree of Parallelism, statement queuing, and in-memory parallel execution will be enabled.
AUTO
Enables automatic degree of parallelism, statement queuing, and in-memory parallel execution.
Incorrect:
C:
LIMITED
Enables automatic degree of parallelism for some statements but statement queuing and inmemory Parallel Execution are disabled. Automatic degree of parallelism is only applied to those statements that access tables or indexes decorated explicitly with the PARALLEL clause. Tables and indexes that have a degree of parallelism specified will use that degree of parallelism.
Reference:Oracle Database VLDB and Partitioning Guide11g,How Parallel Execution Works
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