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How to Read AWR CPU Utilization

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CPU Utilization Breakdown

CPU Utilization

We might have some doubts about OS CPU utilization when we read an AWR report like the following:

CPU Utilization Statistics - from AWR

CPU Utilization Statistics - from AWR

We all may be confused among these components, which are %BUSY, %USER, %SYS, %IOWAIT and %IDLE. To figure them out, we need to know their relationships.

Breakdown Structure

Here is a breakdown structure of CPU utilization components that could help us to read and understand OS statistics more easily.

  • 100 % = %BUSY + %IDLE
  • %BUSY = %USER + %SYSTEM
  • %IDIL = %WIO + (UNDEFINED)

In different OS, the names of these components could vary.

NameAliases
Busy%BUSY, %BUS, %BU
User%USER, %USR, %US
System%SYS, %SY
Wait IO%WIO, %IOWAIT, %WA
Idle%IDLE, %ID