Monitoring Disk I/O Utilization

Because the database resides on a set of disks, the performance of the I/O subsystem is very important to database performance. Important disk statistics include the disk I/Os per second and the length of the service times. These statistics show if the disk is performing optimally or if the disk is being overworked. This section describes how to monitor disk I/O utilization.

To monitor disk I/O utilization: 

1. From the Database Home page, under Host CPU, click the Load link.

   The Host page appears, showing the Performance subpage.

2. Select Disk Details from the View list.

   The Disk Details view appears.

   This view contains disk I/O utilization and service time statistics gathered over the last hour, and the top disk devices ordered by the percentage of time that they were in use.

3. Verify the current disk I/O utilization using the Disk I/O Utilization chart.

   The Disk I/O Utilization chart shows how many disk I/Os are being performed per second. The current value for total I/Os per second is displayed below the chart.

4. Click Total I/Os per Second.

   The Total Disk I/O Per Second page appears.

   This page contains disk utilization statistics and related alerts generated over the last 24 hours.

   If you notice an unexpected spike in this value that is sustained through standard workload hours, then a disk I/O performance problem might exist and should be investigated.

5. Verify the current I/O service time using the Longest I/O Service Time chart.

   The Longest I/O Service Time chart shows the longest service time for disk I/Os in milliseconds. The current value for longest I/O service time is displayed below the chart.

6. Click Longest I/O Service Time.

   The Longest Service Time page appears.

   This page contains I/O service time statistics and related alerts generated over the last 24 hours.

   If you notice an unexpected spike in this value that is sustained through normal workload hours, then a disk I/O performance problem might exist and should be investigated.

7. On the Disk Details page, verify the disk devices in the Top Disk Devices table.

   If a particular disk is busy a high percentage of the time, then this disk should be investigated.

8. If a disk I/O performance problem is identified, you can attempt to resolve the problem by doing the following:

   • Use Oracle Automatic Storage Management (Oracle ASM) to manage database storage.

   • Stripe everything across every disk to distribute I/O.

   • Move files such as archived redo logs and online redo logs to separate disks.

   • Store required data in memory to reduce the number of physical I/Os.