Workload Manager virtual memory limits

Workload Manager (WLM) virtual memory limits provide administrators a means to prevent system degradation or system failure due to excessive paging by providing a virtual memory limit on a class or a process.

When a limit is exceeded, WLM takes action by doing one of the following:
  • killing all processes under the WLM class that exceeded its limit
  • killing only the process that caused the WLM class usage to exceed its limit
  • killing the process that exceeded its process limit
Virtual memory limits can be specified for any user-defined class, any default subclass under a user-defined super class, and the default super class.
For accounting purposes, WLM will only consider the following as virtual memory when determining WLM total class or process usage:
  • heap
  • loader initialized data, BSS, shared library, and privately loaded segments
  • UBLOCK and mmap areas
  • large and pinned user space pages
An administrator can specify a WLM virtual memory limit for a class or for each process in the class. When a class limit is exceeded, WLM can either kill all processes assigned to the class, or only kill the process that caused the limit to be exceeded, depending on whether the vmenforce class attribute is set to class or proc, respectively. The default behavior is to only kill the process that caused the limit to be exceeded. A process limit is killed if the virtual memory use of the process surpasses the limit.