1 Oracle Parallel SQL Part 1 Extracted from the book “Oracle Performance Survival Guide” by Guy Harrison Parallel SQL allows a SQL statement to be processed by multiple threads or processes simultaneously. Today’s widespread usage of dual and quad core processors means that even the humblest of modern computers running an Oracle database will contain more than one CPU. While desktop and laptop computers might have only a single disk device, database server systems typically have database files spread – striped – across multiple independent disk devices. Without parallel technology – when an SQL statement is processed in s erial – a session can only make use of one of these CPUs or disk devices at a time. Parallel processing can improve the performance of suitable SQL statements to a degree which is often not possible by any other method. Parallel processing is available in Oracle Enterprise Edition only. This is first of a series of articles in which we’ll look at how Oracle can parallelize SQL statements and how you can use this facility to improve the performance of individual SQLs or the application as a whole. Understanding parallel SQL ........................................................................................................................................... 2 Parallel performance gains ............................................................................................................................................ 5 Deciding to use parallel processing ................................................................................................................................ 7 Controlling parallel query .......................................................................................................................
