Design and Architecture

Many design-stage decisions affect performance. These include how long a transaction will be, how often data or objects need to be updated, where objects will be located, whether they are persistent and if so, how the persistency is achieved, how data is manipulated, how components interact, and how tightly coupled subsystems are, as well as determining responses to errors, retry frequencies, and alternative routes for solving tasks.

As I mentioned in the last section, the general technique for performance tuning during the analysis and design phases is to predict performance based on the best available data.[92] During the design phase, a great deal of prototype testing is possible, and all such tests should feed data back to help predict the performance of the application. Any predictions indicating a problem with performance should be addressed at the design phase, prior to coding. If necessary, it is better to revisit the analysis and alter specifications rather than leave any indicated performance issues unresolved.

At each stage, part of the design objective should be to predict the performance of the application. (Note that when I refer to the design phase, I include both logical and physical design; physical design is often called architecture.) The design phase usually includes determining the target platforms, and any predictions must be tailored to the limitations of those platforms. This is especially important for embedded Java systems (e.g., ...

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