Performance and query optimization


The goal of database performance tuning is to minimize the response time of your queries and to make the best use of your server's resources by minimizing network traffic, disk I/O, and CPU time. This goal can only be achieved by understanding the logical and physical structure of your data, understanding the applications used on your server, and understanding how the many conflicting uses of your database may impact database performance.

The best way to avoid performance problems is to ensure that performance issues are part of your ongoing development activities. Many of the most significant performance improvements are realized through careful design at the beginning of the database development cycle. To most effectively optimize performance, identify the areas that will yield the largest performance increases over the widest variety of situations and focus your analysis on those areas.

Many of the examples within this publication illustrate a query written through either an SQL or an OPNQRYF query interface. The interface chosen for a particular example does not indicate an operation exclusive to that query interface, unless explicitly noted. It is only an illustration of one possible query interface. Most examples can be easily rewritten into whatever query interface that you prefer.

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