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Commands Reference, Volume 1


chclass Command

Purpose

Change the attributes and resource entitlements of a Workload Management class.

Syntax

chclass -a Attribute=Value {[-a Attribute=Value]...} [ -c | -m | -b KeyWord=Value] [ -d Config_Dir] [ -S SuperClass] Name

Description

The chclass command changes attributes for the class identified by the Name parameter. The class must already exist. To change an attribute, specify the attribute name and the new value with the Attribute=Value parameter. To change a limit or shares value, use option -c for cpu, -m for memory, and -b for disk I/O throughput, with the keyword value in min, softmax, hardmax or shares.

Note: Only the root user can change the attributes of a superclass. Only root or authorized users whose user ID or group ID matches the user name or group name specified in the attributes adminuser and admingroup of a superclass can change the attributes of a subclass of this superclass.

Normally, chclass updates the attributes of a class in the relevant WLM property files, and the modifications are applied to the in-core class definition (active classes) only after an update of WLM using the wlmcntrl command.

If an empty string is passed as the configuration name (Config_dir) with the -d flag, the change applies only to the in-core class attributes, and no property file is updated, making the changes temporary (the change is lost if WLM is stopped and restarted or the system is rebooted).

Attributes

The following attributes can be changed:

Class properties:


tier Specifies the tier value. The tier value for a class is the position of the class in the hierarchy of resource limitation desirability for all classes. A class with a lower tier value will be more favored. The tier value is a number from 0 to 9 (default is 0).
inheritance If inheritance is set to yes, the children of processes in this class remain in the class upon exec regardless of the automatic assignment rules in effect. If inheritance is set to no, the assignment rules apply normally. The default if not specified is no.
localshm Indicates whether memory segments accessed by processes in different classes remain local to the class they were initially assigned to or if they go to the Shared class. The possible value is Yes or No. If not specified, the default is No.
authuser Specifies the user name of the user allowed to assign processes to this class. The default when the attribute is not specified is root.
authgroup Specifies the group name of the group of users allowed to assign processes to this class. There is no default value.
rset Specifies the name of a resource set the processes in the class have access to. The default is that the class has access to all the resources on the system.
adminuser Specifies the user name of the user allowed to administer the subclasses of this superclass. This attribute is valid only for superclasses. The default, when the attribute is not specified is a null string, and, in this case, only root can administer the subclasses.
admingroup Specifies the group name of the group of users allowed to administer the subclasses of this superclass. This attribute is valid only for superclasses. The default value, when the attribute is not specified is a null string, meaning that no group can administer the subclasses.

Class limits and shares for CPU, memory, or disk I/O resource:


min Specifies the minimum percentage of the resource that must be made available when requested, expressed as a percentage of the total resource available in the system. Possible values range from 0 to 100 (default is 0).
shares Specifies the maximum ratio of the resource that can be made available if there is contention. This parameter is expressed in shares of the total resource available in the system. The actual ratio of the resource is dynamically computed, proportionally to the shares of all active classes. If a class has no running process, its shares are excluded from the computation. The shares are arbitrary numbers from 1 to 65535. If shares is specified as hyphen ('-'), this means that the class is always considered on target and that its utilization for this resource is not regulated by WLM, but the minimum and maximum limits if any still apply. This is the default if the shares for a resource are not specified.
softmax Specifies the maximum percentage of the resource that can be made available, when there is contention. Possible values range from 1 to 100 (default is 100). A class can exceed its soft maximum for a given resource if there is no contention on the resource.
hardmax Specifies the maximum percentage of the resource that can be made available, even if there is no contention. Possible values range from 1 to 100 (default is 100). Specifying a value different from the default 100 for memory can result in some memory pages remaining unused, while some processes in the class could use more.
max Specifies the maximum percentage of the resource that can be made available, even if there is no contention. Possible values range from 1 to 100 (default is 100). Specifying a value different from the default 100 for memory can result in some memory pages remaining unused, while some processes in the class could use more.

Note: The default values for a class can be read using lsclass -D and can be changed by manually editing the property files classes, shares, or limits to add a default stanza. See the description of these files in the AIX 5L Version 5.1 Files Reference for details.

Class description:


description The class description text can be composed of any ASCII character, except colon (:) and comma (,).

Flags


-b KeyWord=Value Changes a limit or shares value for disk I/O throughput. Possible KeyWords are min, softmax, hardmax, or shares.
-c KeyWord=Value Changes a limit or shares value for a CPU. Possible KeyWords are min, softmax, hardmax, or shares.
-d Config_Dir Uses the /etc/wlm/Config_Dir directory as alternate directory for the properties files. If this flag is not present, the current configuration files in the directory pointed to by /etc/wlm/current are used. If an empty string is passed as the configuration name (-d "") the modifications only affect the in-core class definition and no configuration file is modified.
-m KeyWord=Value Changes a limit or shares value for memory. Possible KeyWords are min, softmax, hardmax, or shares.
-S SuperClass Specifies the name of the superclass when changing the attributes of a subclass. There are two ways of specifying that the change is to be applied to the subclass Sub of superclass Super:
  1. Specify the full name of the subclass as Super.Sub and not use -S.
  2. Uses the -S flag to give the superclass name and use the short name for the subclass:

    chclass options -S Super  Sub
    

Files


classes Contains the names and definitions of the classes.
limits Contains the resource limits enforced on the classes.
shares Contains the resource shares attributes for each class.

Related Information

The wlmcntrl command, lsclass command, mkclass command, and rmclass command.


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