Which two statements are true about index full scans?

Question

Options

• AAn index fast full scan multi block I/O to read the index structure in its entirely.
• BIndex nodes are not retrieved in the index order, and there fore the nodes are not in sequence.
• CAn index fast full scan reads the index block by block.
• DAn index fast full scan reads the whole index from the lowest value to the higher value.

• A
  78% (18)
• C
  17% (4)
• D
  4% (1)

Explanation

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. there are some requirements for Oracle to invoke the fast full-index scan. All of the columns required must be specified in the index. That is, all columns in the select and where clauses must exist in the index. The query returns more than 10 percent of the rows within the index. This 10 percent figure depends on the degree of multi-block reads and the degree of parallelism. You are counting the number of rows in a table that meet a specific criterion. The fast full- index scan is almost always used for count(*) operations.

No community discussion yet for this question.