| Lesson 5 | Disk I/O and Oracle |
| Objective | Explain the importance of disk I/O to Oracle database performance. |
Disk I/O | Database Performance
One of the critical issues with Oracle database tuning is the time required
to perform an I/O operation on disk. When Oracle requests a data block, this request translates into an OS request for the operating system to
fetch a data block from a disk device.
The Slide Show below illustrates this.
The Slide Show below illustrates this.
1) Input Output 1
2) Input Output 2
3) Input Output 3
4) Input Output 4
5) Input Output 5
6) Input Output 6
7) Input Output 7
8) Input Output 8
9) Input Output 9
The most time consuming of these processes is reading the data block from disk.
I/O Performance Factors
To review, a disk I/O can take several milliseconds, which does not sound like much time, but databases that perform hundreds of I/O per second will suffer a degradation in response time.
The time required to service an I/O (called latency) is the sum of the rotational delay on the disk, the seek delay as the read/write heads position themselves under the proper cylinder, and the data transmission time to the database server.
The time required to service an I/O (called latency) is the sum of the rotational delay on the disk, the seek delay as the read/write heads position themselves under the proper cylinder, and the data transmission time to the database server.
We will devote an entire module to disk I/O, which is the single largest component of OS response time.
The next lesson looks at memory usage in the OS environment.
The next lesson looks at memory usage in the OS environment.
