IBM i automatically tracks many system limits and allows you to review these limits using various IBM i services, such as the
view. There are many monitored categories, such as database, journal, work management and file system limits. See the
topic in the IBM i Knowledge Center for the full list of tracked limits.
For each limit that is tracked, you will find an identifier as well as the maximum allowed value for that particular limit. The floor is the level at which IBM i starts to track that limit, and the increment is how much the usage must change (either increase or decrease) for an entry to be tracked in the QSYS2.SYSLIMTBL table.
Automatically tracking the limits is great, but knowing when a limit is getting near the maximum is essential for the health of your system as well as administrative peace of mind. IBM supports automatic alerting on a subset of the system limits. This automatic alerting is in the form of a message, SQL7062 that is sent to QSYSOPR. By default, the system processes the alerts when Collection Services is cycled, which is typically midnight for most systems.
However, alerting once a day is insufficient if you are dealing with limits approaching their maximum on an ongoing basis. I am working with a client that has such an issue with a large table. This client submitted an idea for more a customizable alerting cadence to IBM. I’m happy to report that IBM delivered this enhancement in the Db2 Group PTF this past December; level 3 for 7.5 and level 23 for 7.4.
This new capability is the QSYS2.PROCESS_SYSTEM_ALERTS procedure. This allows you to call this procedure when you want the system to check for limits that have exceeded their alerting threshold; for example, you could schedule this to be called hourly.
You can also customize the alerting level for a subset of the system limits. IBM documents the default alerting level as well as global variables that can be defined to change the percentage at which the alert is issued. These are documented on the System Limits Alerts page.
Finally, not all limits have alerting in place. For many limits, you must manually check on them or use something like the Adminsitration Runtime Expert SQL Query Verifier to schedule checks where you can query the limit and assess a percentage.
Refer to these previous i Can posts for additional information on system limits:
Introduction to IBM i System Limits and Maximum Capacities
Tracking IBM i System Limits, Part 2
IBM i 7.5: New System Limits and More Hidden Gems
