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To access the contents, click the chapter and section titles.
Oracle Performance Tuning and Optimization
Hardware EnhancementsIn a batch system, several hardware enhancements can help you improve performance. These hardware enhancements can be beneficial in the area of CPU, I/O, and network, as described in the following sections. CPU Enhancements Enhancing the CPUs on your SMP or MPP system can provide instantaneous performance improvementsassuming that you are not I/O bound and that you are taking advantage of the Oracle Parallel Query option. The speed of CPUs is constantly being improved as are new and better cache designs. For SMP or MPP machines, the process of enhancing the CPU may be as simple as adding an additional CPU board. Before you purchase an additional processor of the same type and speed, consider upgrading to a faster processor. Because some batch processing jobs consist of a single job processing the data, you may benefit by purchasing a faster processor rather than more processors. Of course, this depends on your batch jobs and use of the Parallel Query option (refer to Chapter 13, System Processors). SMP and MPP computers provide scaleable CPU performance enhancements at a fraction of the cost of another computer. When upgrading your processors or adding additional processors, remember that your I/O and memory needs will probably increase along with the CPU performance. Be sure to budget for more memory and disk drives when you add processors. I/O Enhancements You can enhance I/O by adding disk drives or purchasing a hardware disk array. Batch processing systems can benefit from the disk striping available in hardware or software disk arrays, but the benefit of the disk array is enhanced by the use of the Parallel Query option. Using Oracle data file striping also helps the performance of your batch processing system. Hardware and software disk arrays have the added benefit of optional fault tolerance. As described in Chapter 15, Disk Arrays, each of the fault-tolerant RAID levels has its advantages and disadvantages. You should first choose the correct fault tolerance for your needs and then make sure that you have sufficient I/O capabilities to achieve the required performance level. If you use fault tolerance, you will most likely have to increase the number of disk drives in your system. Another benefit of hardware disk arrays is caching. Most disk arrays on the market today offer some type of write or read/write cache on the controller. The effect of this cache is to improve the speed of writing to the disk; the cache also masks the overhead associated with fault tolerance. If your queries often perform table scans, you may see good improved performance with disk controllers that take advantage of read-ahead features. Read-ahead occurs when the controller detects a sequential access and reads an entire track (or some other large amount of data) and caches the additional data in anticipation of a request from the OS. Unlike an OLTP system in which this is just wasted overhead, in the batch processing system, it is likely that you will need that data soon; if you do, it will be available very quickly.
Enhancements to the I/O subsystem almost always help in a batch processing environment (as they do with all RDBMS environments). Be sure that you have a sufficient number of disk drives, properly configured. An I/O bottleneck is usually difficult to work around. As with all types of systems, a well-tuned application is very important. Network Enhancements Network performance is never an issue during the actual transaction processing phase of the batch job, but it can be an issue during the load and unload phases of the batch job. Because large amounts of data may be transferred across the wire during these times, a high-speed link is beneficial. You may be able to take advantage of the new 100Base-T technology or you may benefit from a fiber-optics link. The faster the network link, the faster the load/unload happens. You may find it beneficial to install a private link between the batch processing system and the location from which you are loading your data. Try to use the latest technologysuch as 100 megabit Ethernetto provide for future expansion. Miscellaneous Enhancements You may be able to take advantage of other hardware or software enhancements to improve the performance of your batch processing system:
Other miscellaneous enhancements may be available. See what is available on the market and determine whether it can help you.
Performance VerificationTo verify that the changes you have made have positively affected performance, you must develop some sort of test plan. This test plan should be made up of queries very similar toif not exactly the same asthe transactions you use on a daily basis. The closer your tests are to the actual transactions, the more accurate the performance verification is. A good documented test plan allows you not only to verify system performance but to try new things, such as the Parallel Query option, direct write sorts, or some other new feature you may want to implement in the future. The following sections look at what should be tested in the RDBMS and the operating system.
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