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Which two statements are true about index full scans?
A. An index fast full scan multi block I/O to read the index structure in its entirely.
B. Index nodes are not retrieved in the index order, and there fore the nodes are not in sequence.
C. An index fast full scan reads the index block by block.
D. An index fast full scan reads the whole index from the lowest value to the higher value.
Correct Answer: AB
Explanation/Reference:
A:To speed table and index block access, Oracle uses the db_file_multiblock_read_count parameter (which defaults to 8) to aid in getting full-table scan and full-index scan data blocks into the data buffer cache as fast as possible.
B:The index nodes are not retrieved in index order, the rows will not be sequenced.
Note:
there are some requirements for Oracle to invoke the fast full-index scan.
Reference:index fast full scan tips
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