Change Class (CHGCLS)

The Change Class (CHGCLS) command changes the attributes of a class object that was created using the Create Class (CRTCLS) command. The class defines the processing attributes for jobs that use the class. The class used by a job is specified in the subsystem description routing entry used to start the job. If a job consists of multiple routing steps, the class used by each subsequent routing step is specified in the routing entry used to start the routing step.

Any attribute can be changed, except for the public authority attribute. Refer to the Revoke Object Authority (RVKOBJAUT) command and the Grant Object Authority (GRTOBJAUT) command for more information on changing object authorizations.

Restrictions

1. To use this command, you must have:
   • object management (*OBJMGT) and object operational (*OBJOPR) authorities for the class.
   • execute (*EXECUTE) authority for the library in which the class resides.

Parameters

Class (CLS)

Specifies the qualified name of the class.

Note: The following IBM-supplied classes are not valid for this parameter:

• QARBCLS
• QLPINSTALL
• QMONCLS

This is a required parameter.

Qualifier 1: Class

name

Specify the name of the class.

Qualifier 2: Library

*LIBL

All libraries in the thread's library list are searched until a match is found.

*CURLIB

The current library for the thread is used to locate the object. If no library is specified as the current library for the thread, the QGPL library is used.

name

Specify the library where the class is located.

Run priority (RUNPTY)

Specifies the run priority of jobs that use the class. Run priority is a value ranging from 1 (highest priority) through 99 (lowest priority) that represents the priority at which the job competes for the processing unit relative to other jobs that are active at the same time. For multi-threaded jobs, the run priority is also the highest run priority allowed for any thread within the job. Individual threads within the job may have a lower priority.

This value represents the relative, not absolute, importance of the job. For example, a job with a run priority of 25 is not twice as important as one with a run priority of 50.

*SAME

The run priority does not change.

1-99

Specify the run priority of the job that uses this specified class.

Time slice (TIMESLICE)

Specifies the maximum amount of processor time (in milliseconds) given to each thread in a job using this class before other threads in a job or other jobs are given the opportunity to run. The time slice establishes the amount of time needed by a thread in a job to accomplish a meaningful amount of processing. At the end of the time slice, the thread might be put in an inactive state so that other threads can become active in the storage pool.

*SAME

The time slice does not change.

0-9999999

Specify the maximum amount of time (in milliseconds) that each thread in a job that uses this class can have to run.

Note: Although you can specify a value of less than 8, the system takes a minimum of 8 milliseconds to run a process. If you display a job's run attributes, the time slice value is never less than 8.

Eligible for purge (PURGE)

Specifies whether the job is eligible to be moved out of main storage and put into auxiliary storage at the end of a time slice or when there is a long wait (such as waiting for a work station user's response). The operating system no longer uses this parameter.

*SAME

The value does not change.

*YES

The job is eligible to be moved out of main storage and into auxiliary storage. However, a job with multiple threads is never purged from main storage.

*NO

The job is not eligible to be moved out of main storage and put into auxiliary storage. However, when main storage is needed, pages belonging to a thread in this job may be moved to auxiliary storage. Then, when a thread in this job runs again, its pages are returned to main storage as they are needed.

Default wait time (DFTWAIT)

Specifies the default maximum time (in seconds) that a thread in the job waits for a system instruction, such as the LOCK machine interface (MI) instruction, to acquire a resource. This default wait time is used when a wait time is not specified for a given situation. Normally, this would be the amount of time the system user is willing to wait for the system before the request is ended.

If the wait time for an instruction is exceeded, an error message can be displayed or it can be automatically handled by a Monitor Message (MONMSG) command.

*SAME

The default wait time does not change.

*NOMAX

There is no maximum wait time.

0-9999999

Specify the maximum time (in seconds) that the system waits for the system instruction to acquire a resource.

Note: Although a 0 default wait time is allowed, it is not recommended. Some system instructions require the use of system resources that may be in use and with a 0 default time, will cause the instruction to fail. When a system instruction fails (exceeds the default wait time) unexpected results may occur for the thread. Most system resources will only be in use for a short time, so having a small default wait time will not noticeably degrade the performance of the thread.

Maximum CPU time (CPUTIME)

Specifies the maximum processing unit time (in milliseconds) that the job can use. If the job consists of multiple routing steps, each routing step is allowed to use this amount of processing unit time. If the maximum time is exceeded, the job is held.

*SAME

The maximum processing unit time does not change.

*NOMAX

There is no limit on the processing unit time used.

1-9999999

Specify the maximum amount of processing unit time (in milliseconds) that can be used.

Maximum temporary storage (MAXTMPSTG)

Specifies the maximum amount of temporary (auxiliary) storage (in megabytes) that the job can use. If the job consists of multiple routing steps, this is the maximum temporary storage that the routing step can use. This temporary storage is used for storage required by the program itself and by implicitly created internal system objects used to support the job. (It does not include storage for objects in the QTEMP library.) If the maximum temporary storage is exceeded, the job is held. This parameter does not apply to the use of permanent storage, which is controlled through the user profile.

*SAME

The maximum amount of temporary storage for jobs using this class does not change.

*NOMAX

The system maximum is used.

1-2147483647

Specify the maximum amount of temporary storage (in megabytes) that can be used.

Maximum threads (MAXTHD)

Specifies the maximum number of threads that a job using this class can run with at any time. If multiple threads are initiated simultaneously, this value may be exceeded. If this maximum value is exceeded, the excess threads will be allowed to run to their normal completion. Initiation of additional threads will be inhibited until the maximum number of threads in the job drops below this maximum value.

*SAME

The value does not change.

*NOMAX

There is no maximum number of threads.

1-32767

Specify the maximum number of threads for a job.

Note: Depending upon the resources used by the threads and the resources available on the system, the initiation of additional threads may be inhibited before this maximum value is reached.

Text 'description' (TEXT)

Specifies the text that briefly describes the object.

*BLANK

No text is specified.

'description'

Specify no more than 50 characters of text, enclosed in apostrophes.

Examples

CHGCLS   CLS(CLASS1)  RUNPTY(60)  TIMESLICE(900)

This command changes a class called CLASS1 in the library on the job's library list. The run priority for the class is changed to 60 and a time slice of 900 milliseconds.

Error messages

*ESCAPE Messages

CPF1169

Class &1 in library &2 not changed.