A bitmap join index is simply the bitmap index of a join of two or
more tables. The speedup in performance comes from avoiding actual table joins or
reducing the amount of data joined by taking into account restrictions in advance of
the joining of data. Performance speedup for star queries with multiple dimension
tables can be greatly improved since bitwise operations in star transformations can
now be eliminated.
Performing queries in parallel also obviously improves performance. Joins and sorts
are frequently used to solve decision-support queries. Parallelism is described in
Chapter 7. That chapter lists functions that Oracle can perform in parallel (see
???What Can Be Parallelized????).
Real Application Clusters, which replaced Oracle Parallel Server as of Oracle9i, further
expands parallelism by enabling queries to transparently scale across nodes in
clusters or in grids of computer systems.
Remember that these Oracle features use the cost-based optimizer
and, prior to Oracle Database 10g, you should run statistics periodically
(using the ANALYZE command) on the tables to ensure good
performance.
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