Installation guide

A database must be conﬁgured before you can enable class scheduling with

the enable command. If a database does not exist when you enter the

class_admin command, the command will invoke an interactive session

and prompt you to conﬁgure a database. If the class_admin command is

invoked by a script, a database is conﬁgured automatically, using the

system defaults.

The following example shows an interactive conﬁguration session using

class_admin. Note that in the actual output, the lines will be formatted to

ﬁt in 80 columns:

# /usr/sbin/class_admin

Class Scheduler Administration

configure:

Shall processes that have not been explicitly

assigned to a defined class be assigned to a

’default’ class? Enter (yes/no) [no]: yes

Enforce class scheduling when the CPU is otherwise

idle? (yes/no) [no]: yes

How often do you want the system to reset class usage?

Enter number of seconds (1): 2

class>

The conﬁguration values have the following effect:

• To be scheduled, a process must be assigned to a class. If you answer

yes to the ﬁrst prompt, a special class called the default class is

created. Any process that has not been explicitly assigned to a deﬁned

class will be assigned to the default class.

If you answer no to this prompt, then only those processes which are

explicitly assigned to a deﬁned class will be class scheduled.

• If you answer yes to the second prompt, you allow classes to exceed

their allotted CPU time percentage when the system is otherwise idle.

If you answer no , classes are restricted to their allotted percentage

even if the CPU has no other work.

• The third prompt allows you to set the standard reset time for all

classes. For example, if you choose the short default time of 1 second,

each class will have more frequent, but shorter opportunities to access

the CPU.

Use a small number (several seconds) if there are interactive jobs

subject to class scheduling to give them a quick response time. If only

batch jobs are class scheduled, response time is not an issue and larger

values may be used.

4–30 Customizing the System Environment