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Lesson 1

Tuning disk IO (Intro)

Tuning disk I/O

As we discussed in previous lessons, tuning of disk I/O within an Oracle environment is the single most important thing that you can do in terms of tuning your Oracle database. The purpose of this module is to explain disk I/O its most basic level, and then move forward to take a look at disk I/O tuning and load balancing within your Oracle environment. This module is going to be taking a look at various techniques that you can use in order to balance the load amongst all of your different systems. Again, it's very important to remember that this is probably the most important module in the entire performance and tuning series so let's get started.

Tuning disk I/O within Oracle environment to influence performance

Tuning of disk I/O within an Oracle environment can have a significant impact on performance, as disk I/O is often the bottleneck for many databases. The following are some ways to tune disk I/O within an Oracle environment:
  1. Proper disk layout: Properly laying out the Oracle data files, log files, and control files on different physical disks can help to spread the I/O load across multiple disks, which can improve performance.
  2. Striping: Striping the data files across multiple disks can also improve performance by allowing the database to read and write data in parallel.
  3. RAID: Using RAID (Redundant Array of Independent Disks) can provide a performance boost by allowing the database to read and write data in parallel, as well as providing data redundancy in case of disk failure.
  4. Caching: Enabling caching on the storage array can help to reduce the number of disk I/O operations, by keeping frequently accessed data in memory.
  5. Tune the Oracle parameters: Oracle parameters such as db_file_multiblock_read_count, db_writer_processes, and db_block_size can affect the disk I/O performance and need to be tuned accordingly.
  6. Monitor disk I/O: Monitoring disk I/O using tools like Oracle's Automatic Workload Repository (AWR) and the Operating System's performance monitoring tools can help to identify and diagnose performance bottlenecks.

It is important to note that tuning disk I/O should be done in conjunction with other performance tuning activities, such as memory and CPU tuning, to achieve optimal performance.

The time required to fetch data blocks from disk can be a large component of total response time. A tremendous amount of work has been done to ensure that disk I/O is minimized within Oracle. Nevertheless, a request from Oracle to get a row may ultimately result in a disk I/O. This module describes techniques for measuring disk I/O and looks at disk load balancing and striping techniques.
By the end of this module you will be able to:
  1. Execute and interpret iostat
  2. Define a hot disk
  3. Identify files that are causing high I/O
  4. Stripe a data file
  5. Explain OS file striping techniques
  6. Stripe a table with PCTFREE
The next lesson presents an overview of the iostat utility.