D the optimizer does not monitor cardinality feedback

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D. The optimizer does not monitor cardinality feedback if dynamic sampling and multicolumn statistics are enabled. E. After the optimizer identifies a query as a re-optimization candidate, statistics collected by the collectors are submitted to the optimizer. Correct Answer: ACD Section: (none) Explanation Explanation/Reference: Explanation: C: During the first execution of a SQL statement, an execution plan is generated as usual. D: if multi-column statistics are not present for the relevant combination of columns, the optimizer can fall back on cardinality feedback. (not B)* Cardinality feedback. This feature, enabled by default in 11.2, is intended to improve plans for repeated executions. optimizer_dynamic_sampling optimizer_features_enable * dynamic sampling or multi-column statistics allow the optimizer to more accurately estimate selectivity of conjunctive predicates. Note: * OPTIMIZER_DYNAMIC_SAMPLING controls the level of dynamic sampling performed by the optimizer. Range of values. 0 to 10 * Cardinality feedback was introduced in Oracle Database 11gR2. The purpose of this feature is to automatically improve plans for queries that are executed repeatedly, for which the optimizer does not estimate cardinalities in the plan properly. The optimizer may misestimate cardinalities for a variety of reasons, such as missing or inaccurate statistics, or complex predicates. Whatever the reason for the misestimate, cardinality feedback may be able to help. QUESTION 102 Which three statements are true when the listener handles connection requests to an Oracle 12c database instance with multithreaded architecture enabled In UNIX? (Choose three.) A. Thread creation must be routed through a dispatcher process B. The local listener may spawn a now process and have that new process create a thread C. Each Oracle process runs an SCMN thread. D. Each multithreaded Oracle process has an SCMN thread. E. The local listener may pass the request to an existing process which in turn will create a thread.
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Correct Answer: ADE Section: (none) Explanation Explanation/Reference: Explanation: QUESTION 103 Which three operations can be performed as multipartition operations in Oracle? (Choose three.) A. Merge partitions of a list partitioned table B. Drop partitions of a list partitioned table C. Coalesce partitions of a hash-partitioned global index. D. Move partitions of a range-partitioned table E. Rename partitions of a range partitioned table F. Merge partitions of a reference partitioned index Correct Answer: ABF Section: (none) Explanation Explanation/Reference: Explanation: Multipartition maintenance enables adding, dropping, truncate, merge, split operations on multiple partitions. A: Merge Multiple Partitions: The new “ALTER TABLE … MERGE PARTITIONS ” help merge multiple partitions or subpartitions with a single statement. When merging multiple partitions, local and global index operations and semantics for inheritance of unspecified physical attributes are the same for merging two partitions.
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  • Fall '19
  • Oracle Database

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