You can monitor the status of the z/OS UNIX system and process limits with the D OMVS, LIMITS operator command and console messages that indicate when limits are reaching critical levels. Use SET OMVS or SETOMVS to change certain system limits dynamically, or SETOMVS with PID= to change a process-level limit for a specific process.

The LIMMSG statement in BPXPRMxx controls message activity for limits checking. You can specify whether no console messages are to be displayed when any of the parmlib limits have been reached (NONE); console messages are to be displayed for all processes that reach system limits and for certain process limits (SYSTEM); or console messages are to be displayed for all the system limits and the process limits (ALL).

The LIMMSG options can be changed with the SETOMVS LIMMSG command. The LIMMSG value appears in the D OMVS,O display.

If the LIMMSG statement is specified with SYSTEM or ALL, a warning console message appears whenever a limit reaches 85%, 90%, 95%, and 100%, identifying the process that has reached the limit. When the limit reaches the next limit level, the prior message is removed from the console and a new message indicates the new limit level that has been reached. When the limit falls below the 85% threshold, a message indicates that the resource shortage has been relieved.

For limit MaxSharePages, the first warning message appears at 60% to warn the installation when copy-on-write (COW) processing for fork() is about to be disabled (which occurs at a usage of 62.5%). This message is replaced when the next limit is reached or removed from the console when the limit falls under 60%.

Example: BPXI039I SYSTEM LIMIT MAXSHAREPAGES HAS REACHED 60% OF ITS CURRENT CAPACITY OF 4096

Changing from LIMMSG(ALL) or LIMMSG(SYSTEM) to LIMMSG(NONE) with the SETOMVS command stops any further monitoring of resources. However, existing outstanding messages are not deleted from the screen for a process until the limit is relieved for that process.

Tip: When LIMMSG(ALL) is in effect, a large number of messages can be issued. This option is best suited for use during the initial configuration of a system, when the installation has not yet determined the optimal settings for the z/OS UNIX parmlib limits.