JOBCLASS Parameter

Purpose

The JOBCLASS parameter (or simply CLASS parameter on the JOB statement) specifies the job class for the job. Job classes are used to group jobs with similar resource requirements, execution characteristics, and scheduling needs. This parameter helps system administrators manage system workload, prioritize jobs, and apply specific execution rules to groups of similar jobs.

Syntax

On JOB Statement

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//jobname JOB accounting-info,programmer-name,CLASS=class

Abbreviated form:

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//jobname JOB accounting-info,programmer-name,CLASS=c

Parameter Components

class

A single character (A-Z, 0-9, or *) that identifies the job class. The class defines processing attributes such as:

• System resources available to the job
• Execution priority
• Output handling characteristics
• Accounting requirements
• Security constraints

Job Class Definitions

Job classes are defined by the system administrator through JES2 or JES3 initialization parameters. While specific meanings vary by installation, some common conventions include:

Key Points

• If you omit the CLASS parameter, the system assigns a default class (usually A).
• The job class often determines the output class for job messages (MSGCLASS).
• Certain job classes may be restricted to specific users or groups.
• Some job classes may only be available during specific time periods.
• Job class can affect job scheduling, execution priority, and resource limits.
• JES2 and JES3 may have different class definitions and behaviors.

JES2 Job Class Attributes

In JES2, job classes can have various attributes defined, including:

• ACTIVE=YES|NO - Whether the class is currently accepting jobs
• JCOPY=MAX|count - Maximum number of job output copies
• OUTDISP=disposition - Default output disposition
• PRTY=priority - Default job priority
• QAFF=sysid - System affinity (which systems can process jobs in this class)
• XBATCH=YES|NO - Whether jobs in this class require special handling

JES3 Job Class Attributes

In JES3, job classes (or "job class groups") can have attributes like:

• SDEPTH=count - Maximum number of jobs that can run concurrently
• TDEPTH=count - Maximum number of jobs that can be scheduled
• MLIMIT=value - Default main storage limit
• SYSTEM=sysname - Eligible systems for job execution
• JOURNALING=YES|NO - Whether to enable journaling
• SPART=partition - Spool partition to use

Examples

Basic Usage

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//PAYROLL  JOB (ACCT123),'JOHN SMITH',CLASS=P

This job will run in class P, which might be a high-priority production class at the installation.

Combined with Other JOB Parameters

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//TESTJOB  JOB (ACCT123),'JANE DEV',CLASS=T,
//             MSGCLASS=X,MSGLEVEL=(1,1),NOTIFY=&SYSUID

This test job runs in class T, sends messages to output class X, sets message level options, and notifies the submitter when the job completes.

Default Class Example

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//REPORT   JOB (ACCT123),'JANE DEV',MSGCLASS=A

Since the CLASS parameter is omitted, this job will execute in the default class (typically A).

Class Selection Considerations

When selecting a job class, consider:

Resource Requirements

• CPU-intensive jobs may require specific classes
• I/O-intensive jobs might need classes with different I/O priorities
• Large memory requirements might demand special classes

Execution Time

• Long-running jobs often need different classes than short jobs
• Time-sensitive jobs may require high-priority classes

Job Type

• Production vs. test jobs
• Online vs. batch processing
• Development vs. QA vs. production environments

Best Practices

1. Always use the appropriate job class based on your installation's standards.
2. Don't use privileged job classes without authorization.
3. For test jobs, use designated test classes to avoid impacting production work.
4. Document the class used in job documentation for maintenance purposes.
5. Understand the resource implications of different job classes in your environment.
6. Be aware that changing a job's class can significantly affect its execution characteristics and priority.