July 2017
Intermediate to advanced
896 pages
23h 12m
English
Content preview from Oracle Internals
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Chapter 49
Oracle Parallel Query
Donald K. Burleson
One of the most exciting performance features of Oracle Version 7.3 and above is the ability to partition an SQL query into subqueries and dedicate separate processors to concurrently service each subquery. At this time, parallel query is useful only for queries that perform full-table scans on long tables, but the performance improvements can be dramatic. Here is how it works.
Parallel queries are most useful in distributed databases where a single logical table has been partitioned into smaller tables at each remote node. For example, a customer table that is ordered by customer name may be partitioned into a customer table at each remote database such that we have a phoenix_customer, a los_angeles_customer, ...
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