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Lesson 8

Operating System Tuning Conclusion

This module has provided a high-level overview of the external OS environment for Oracle databases.

Module summary

Here are the main points from this module.
  1. Disk I/O is the largest component of response time for any Oracle database.
  2. The iostat utility can be used to measure I/O against physical disks.
  3. Iostat information can be stored in Oracle tables for analysis.
  4. Disks that have a disproportional amount of I/O become hot.
  5. The iostat utility can be used to identify hot disks.
  6. In some cases hot disks can lead to I/O bottlenecks.
  7. Once a hot disk is identified, the DBA must learn which Oracle data files reside on that disk.
  8. A physical disk is mapped onto UNIX filesystems or mount points.
  9. The bstat-estat utility can be run to see that data files are active during a specific period.
  10. Hot files should be moved onto less active data disks.
  11. Striping can be used to move a single hot data file into multiple data files.
  12. OS striping can be used to evenly spread data files across disks.
  13. Small, highly active tables can be spread across data blocks by making PCTFREE small

How can the iostat utility be used to measure I/O against physical disks in Oracle?

The iostat utility is a performance monitoring tool that is included with many Unix-based operating systems, including Linux and Solaris. It can be used to measure I/O (input/output) against physical disks in an Oracle database. Here's how to use iostat to measure I/O against physical disks in Oracle:
  1. Open a terminal window on the Oracle database server.
  2. Type "iostat -x" to run the iostat utility in extended mode. The "-x" option displays detailed disk I/O statistics, including the number of read and write operations, the number of kilobytes read and written, and the percentage of CPU time spent on I/O.
  3. Press Enter to execute the command.
  4. Monitor the output of iostat to see the I/O performance of the physical disks on the Oracle database server. Look for high values in the "rkB/s" and "wkB/s" columns, which indicate high disk I/O activity.
  5. Identify the physical disks that are experiencing high I/O activity by looking at the "Device" column. Note the device name, such as "sda" or "sdb".
  6. Use the Oracle Enterprise Manager (OEM) or the command-line tool "iostat" with the "-d" option to identify which Oracle database files are mapped to the high I/O physical disks. For example, you can type "iostat -d -x /dev/sda" to display I/O statistics for the physical disk "sda" and identify which database files are mapped to that disk.
  7. Use this information to optimize the I/O subsystem for the Oracle database. This may include adding more physical disks, configuring RAID, tuning the disk scheduler, or tuning the buffer cache.

In summary, the iostat utility can be used to measure I/O against physical disks in an Oracle database. By monitoring the I/O performance of physical disks and identifying the database files that are mapped to them, DBAs can optimize the I/O subsystem for the Oracle database and improve performance.

Now you should be able to:
  1. List OS components that can be tuned
  2. Describe OS tuning roles
  3. Explain the architecture-related performance factors
  4. Explain the importance of disk I/O to Oracle database performance
  5. Describe how OS memory is managed
  6. Describe how Oracle manages CPU usage


Here are some terms from this module that may be new to you:
  1. latency: The time required to service an I/O.
  2. page in: Re-loading swapped-out memory from disk to RAM.
  3. swap disk: Special disk reserved for memory paging operations.
  4. heap: The name for the memory region on the host.

OS Issues Quiz

Click the Quiz link below to test your knowledge of the concepts you learned in this module.
OS Issues - Quiz