Identify the benefit of using bitmap join indexes. Select one.
A.
Faster query performance for all queries.
B.
Reduced space for indexes.
C.
Faster query performance for some queries.
D.
Lower memory usage.
Explanation:
Oracle benchmarks claim that bitmap join indexes can run a query more than eight times faster
than traditional indexing methods.
However, this speed improvement is dependent upon many factors, and the bitmap join is not a
panacea. Some restrictions on using the bitmap join index include:
The indexed columns must be of low cardinalityusually with less than 300 distinct values.
The query must not have any references in the WHERE clause to data columns that are not
contained in the index.
The overhead when updating bitmap join indexes is substantial. For practical use, bitmap join
indexes are dropped and rebuilt each evening about the daily batch load jobs. This means that
bitmap join indexes are useful only for Oracle data warehouses that remain read-only during the
processing day.
Reference:
http://www.dba-oracle.com/art_builder_bitmap_join_idx.htm
Isn’t it c ?
B,
Oracle’s two major index types are Bitmap indexes and B-Tree indexes. B-Tree indexes are the regular type that OLTP systems make much use of, and bitmap indexes are a highly compressed index type that tends to be used primarily for data warehouses.