IBM i Recipes

1. CPU core(s) should not be consistently saturated.
2. Generally, physical memory should never be saturated and the operating system should not page memory out to disk.
3. Input/Output interfaces such as network cards and disks should not be saturated, and should not have poor response times.
4. TCP/IP and network tuning, whilst sometimes complicated to investigate, may have dramatic effects on performance.
5. Operating system level statistics and optionally process level statistics should be periodically monitored and saved for historical analysis.
6. Review operating system logs for any errors, warnings, or high volumes of messages.
7. Review snapshots of process activity, and for the largest users of resources, review per thread activity.
8. If the operating system is running in a virtualized guest, review the configuration and whether or not resource allotments are changing dynamically.
9. Enable Collection Services for performance data.
10. If there is sufficient network capacity for the additional packets, consider reducing the default TCP keepalive timer (CHGTCPA TCPKEEPALV) from 2 hours to a value less than intermediate device idle timeouts (e.g. firewalls).
11. Test disabling delayed ACKs

For details, see the IBM i chapter.

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