CPU utilization

Estimates of CPU utilization and response time can help you determine if you need to eliminate or reschedule some activities.

You can use the resource-utilization formula in the previous topic (Resource utilization) to estimate the response time for a heavily loaded CPU. However, high utilization for the CPU does not always indicate a performance problem. The CPU performs all calculations that are needed to process transactions. The more transaction-related calculations that it performs within a given period, the higher the throughput will be for that period. As long as transaction throughput is high and seems to remain proportional to CPU utilization, a high CPU utilization indicates that the computer is being used to the fullest advantage.

On the other hand, when CPU utilization is high but transaction throughput does not keep pace, the CPU is either processing transactions inefficiently or it is engaged in activity not directly related to transaction processing. CPU cycles are being diverted to internal housekeeping tasks such as memory management.

You can easily eliminate the following activities:
  • Large queries that might be better scheduled at an off-peak time
  • Unrelated application programs that might be better performed on another computer

If the response time for transactions increases to such an extent that delays become unacceptable, the processor might be swamped; the transaction load might be too high for the computer to manage. Slow response time can also indicate that the CPU is processing transactions inefficiently or that CPU cycles are being diverted.

When CPU utilization is high, a detailed analysis of the activities that the database server performs can reveal any sources of inefficiency that might be present due to improper configuration. For information about analyzing database server activity, see Database server tools.


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