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To access the contents, click the chapter and section titles.
Oracle Performance Tuning and Optimization
Server OS TuningYou may have to tune the server OS to provide for optimal I/O performance. Some of the things you may have to tune in the server OS are listed here; remember that some OSes may not require any tuning in these areas:
The server operating system is mainly a host on which Oracle does its job. Any work done by the operating system is essentially overhead for Oracle. By optimizing code paths and reducing OS overhead, you can enhance Oracle performance. EnhancementsYou may want to make some additional enhancements to improve the performance of your system. Listed here are some of the items that can offer performance improvement; also listed are a few items that do not improve performance. Each item is accompanied by an explanation.
Some of these enhancements can help your performance. The specific effect on your system will vary, but the information given here is true for most general cases. Hardware EnhancementsIn a BLOB 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 your application is causing the system to become CPU bound. 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. In this type of environment, both the addition of faster processors and more processors benefit the overall performance of the system. I/O Enhancements You can enhance I/O by adding disk drives or purchasing a hardware disk array. Systems that access BLOB data can benefit from the disk striping available in both hardware and software disk arrays. Using Oracle data file striping can also help the performance of this type of 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 BLOB system, you will need that data soon; if it is in the cache, it will be available very quickly.
Enhancements to the I/O subsystem make all the difference in the world to a BLOB environment because large amounts of data are being continually read. 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.
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