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Oracle Performance Tuning with AWR: Understanding How Oracle Calculates Host CPU Usage

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Monitoring host CPU usage is crucial for Oracle database performance. Here’s how Oracle calculates it using Operating System Statistics over a 29.62-minute snapshot with 80 CPUs.

Total CPU Time:

  • Elapsed time: 29.62 minutes = 1,777.2 seconds.
  • Total CPU time: 1,777.2 × 80 = 142,176 seconds.
  • From OS Stats: BUSY_TIME (1,905,713) + IDLE_TIME (12,222,778) = 14,128,491 hundredths = 141,284.91 seconds.

Host CPU Metrics: Using the total CPU time (14,128,491 hundredths of a second):

  • %Idle: (12,222,778 / 14,128,491) * 100 = 86.5%
  • %User: (1,560,943 / 14,128,491) * 100 = 11.0%
  • %System: (224,397 / 14,128,491) * 100 = 1.6%
  • %WIO (I/O Wait): (569,321 / 14,128,491) * 100 = 4.0%

Note: IOWAIT_TIME is part of IDLE_TIME, so don’t double-count it.

These metrics help DBAs assess host-level CPU utilization. Stay tuned for our next post on Oracle instance CPU usage!

One response to “Oracle Performance Tuning with AWR: Understanding How Oracle Calculates Host CPU Usage”

  1. Understanding How Oracle Calculates Instance CPU Usage – Yuan Yao, An Oracle ACE's Blog avatar
    Understanding How Oracle Calculates Instance CPU Usage – Yuan Yao, An Oracle ACE's Blog

    […] our previous article, we discussed How Oracle Calculates Host CPU Usage. Now we’ll explore Oracle instance CPU […]

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