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Files Reference

Workload Manager limits File


Describes the minimum and maximum limits for the resources allocated to superclasses or subclasses of a WLM configuration.


The limits file in the /etc/wlm/Config describes the resource limits for the superclasses of the WLM configuration Config. If the superclass Super of this configuration has subclasses defined, the resource limits for the subclasses are defined in the file /etc/wlm/Config/Super/limits.

The limits at the superclass level represent a percentage of the total amount of resources available on the system and the limits at the subclass level represent a percentage of the resource made available to the parent superclass. Despite this difference, the description of resource limits is relevant to both a superclass and a subclass.

The limits file is organized into stanzas that are named after WLM classes and contain attribute-value pairs specifying the minimum and maximum resource limit allocated to the class for the various resources. The attribute names identify the resource. For each resource, the following values must be provided:

The limits are expressed as percentages. Both the minimum and maximum limits are each a number between 0 and 100. The hard maximum must be greater than or equal to the soft maximum, which in turn must be greater than or equal to the minimum. When the limits are not specified for a class or a resource type, the system defaults to 0 for the minimum and 100 for both the soft and hard maximum.

Use the following format for defining the limit values:

attribute_name = m%-SM%,HM%


Each stanza names a WLM class that must exist in the classes file at the corresponding level (superclass or subclass).

The following attributes are defined in the limits file:

CPU Represents the CPU limits for the class
memory Represents the physical memory limits for the class
diskIO Represents the disk I/O limits for the class

The default values mentioned above are the system defaults and can be modified using a special stanza named "default."

Consider the following stanza at the beginning of the limits file:

   CPU   = 10%-50%,80%
   diskIO  = 20%-60%,100%

This stanza modifies the default values of the limits for CPU and disk I/O so that if those attributes are not specified for some (or all) of the classes, their minimum, soft maximum, and hard maximum default to the values shown above. In this example, the default values for the physical memory limits (specified by the memory attribute) are still the system default--the minimum 0% and the soft and hard maximum each 100%.

Classes that use only default values for all the resource types can be omitted in the file.


The limits file defining the limits of the superclasses of a WLM configuration must have write permission for root only. The limits file defining the limits for the subclasses of a superclass must have write permission for the adminuser and admingroup for the superclass. If no adminuser exists for the superclass, the limits file should be owned by root. If no admingroup exists for a superclass, the file for the superclass should be owned by the "system" group and have no write permission for group.


The following is an example of a typical /etc/wlm/Config/limits file:

* System Defined Classes
* In this example, the system administrator uses
* only default values for the System and Shared
* superclasses. The System class has a memory minimum of
* 1% by default - can be increased by system administrator
* The system administrator gives non default values
* only for the Default class:
   memory = 1%-100%,100%
   CPU    =  0%-50%,75%
   memory = 0%-25%,50%
* User defined classes
   CPU     = 10%-100%,100%
   memory  = 20%-100%,100%
   diskIO = 0%-33%,50%
   memory  =0%-20%,50%
   diskIO =10%-66%,100%

Note: The asterisk (*) is a comment character.

Implementation Specifics

This file is part of Base Operating System (BOS) Runtime.


limits Defines the resource entitlements for the superclasses or subclasses of a WLM configuration

Related Information

The lsclass command, mkclass command, chclass command, rmclass command.

The classes file, shares file, rules file.

Chapter 6. Files in AIX 5L Version 5.1 System User's Guide: Operating System and Devices.

Chapter 13. Workload Manager in AIX 5L Version 5.1 System Management Concepts: Operating System and Devices


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