The optimizer chooses intelligent defaults for the degree of parallelism based on available processors and the number of disk drives storing data the query will access. Execution plans are more scalable, and there is improved correlation between optimizer cost and execution time for parallel query. Parallel Query Oracle8 Server provides for improved performance through use of parallel data manipulation language. The parallel query feature enables multiple processes to work together simultaneously to process a single query. By dividing the task among multiple server processes, Oracle can execute a SQL statement more quickly than if only one server process were used.
Parallel query can dramatically improve performance for data-intensive data warehousing operations.
It helps systems scale in performance when adding hardware resources. Bitmap Indexes Regular B tree indexes work best when each key or key range references only a few records, such as employee names. Bitmap indexes, by contrast, work best when each key references many records, such as employee gender. Bitmap indexing provides the same functionality as regular indexes, but uses a different internal representation, which makes it very fast and space efficient. Bitmap indexing benefits data warehousing applications which have large amounts of data and ad hoc queries, but a low level of concurrent transactions.