1Z0-083 · Question #209
Which two are true about Oracle Optimizer Statistics, their use, and their collection? (Choose two.)
The correct answer is B. Index balanced B*Tree height is considered when evaluating the cost of using an index. C. The Statistics Advisor can help recommend the best way to gather statistics. https://docs.oracle.com/database/121/TGSQL/tgsql_optcncpt.htm#TGSQL218 B is correct. The cost of an index scan depends on the levels in the B-tree, the number of index leaf blocks to be scanned, and the number of rows to be fetched using the rowid in the index keys. The cost of…
Question
Which two are true about Oracle Optimizer Statistics, their use, and their collection? (Choose two.)
Options
- AThe number of table rows is considered when evaluating the cost of accessing a table using
- BIndex balanced B*Tree height is considered when evaluating the cost of using an index.
- CThe Statistics Advisor can help recommend the best way to gather statistics.
- DStatistics collected using DBMS_STATS always yield the best optimizer result.
- EThe Statistics Advisor generates actions for all recommendations.
How the community answered
(15 responses)- A7% (1)
- B87% (13)
- D7% (1)
Explanation
https://docs.oracle.com/database/121/TGSQL/tgsql_optcncpt.htm#TGSQL218 B is correct. The cost of an index scan depends on the levels in the B-tree, the number of index leaf blocks to be scanned, and the number of rows to be fetched using the rowid in the index keys. The cost of fetching rows using rowids depends on the index clustering factor. C is correct. The output of the advisor is a report of findings and recommendations, which helps you follow best practices for gathering statistics.
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