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 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.
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.