How To Craft Control Cards In Mainframe: The Ultimate Beginner’s Guide

In the realm of mainframe computing, control cards play a pivotal role in directing the execution of jobs and managing system resources. Understanding how to create control cards is essential for anyone working with mainframes. This comprehensive guide will delve into the intricacies of creating control cards, providing step-by-step instructions and insightful explanations.

What is a Control Card?

A control card is a special type of input card that provides instructions to the operating system (OS) regarding the execution of a job. It contains information such as the job name, job class, resource requirements, and the commands to be executed.

Creating a Control Card

1. Start with a Job Statement

Every control card begins with a job statement, which identifies the job and specifies its parameters. The general syntax is:

“`
//jobname JOB,jobclass,parameters
“`

For example:

“`
//MYJOB JOB,A,TIME=10
“`

2. Define Resource Requirements

The resource requirements section specifies the amount of memory, CPU time, and other resources required by the job. The syntax is:

“`
REGION=sizeK,TIME=time
“`

For example:

“`
REGION=1024K,TIME=15
“`

3. Specify the Execution Command

The execution command specifies the program or command to be executed. The syntax is:

“`
EXEC PGM=program-name,PARM=parameters
“`

For example:

“`
EXEC PGM=MYPROGRAM,PARM=A,B,C
“`

4. Define Input and Output Files

The input and output files section specifies the files to be used as input and output for the job. The syntax is:

“`
DDname DD UNIT=device-type,DISP=disposition
“`

For example:

“`
INFILE DD UNIT=SYSDA,DISP=SHR
OUTFILE DD UNIT=SYSDA,DISP=(NEW,DELETE)
“`

5. Add Additional Parameters

Additional parameters can be added to the control card to further customize the job’s execution. These parameters include:

• MSGLEVEL: Specifies the level of messages to be displayed during job execution.
• NOTIFY: Specifies the user to be notified when the job completes.
• COND: Specifies conditions that must be met before the job can execute.

6. End with a /* Statement

Every control card must end with a /* statement, which indicates the end of the job.

“`
/*
“`

7. Submit the Control Card

Once the control card is complete, it can be submitted to the operating system using the SUBMIT command.

Example: A Simple Control Card

“`
//MYJOB JOB,A,TIME=10
//INFILE DD UNIT=SYSDA,DISP=SHR
//OUTFILE DD UNIT=SYSDA,DISP=(NEW,DELETE)
//EXEC PGM=MYPROGRAM,PARM=A,B,C
/*
“`

This control card will execute the program MYPROGRAM with parameters A, B, and C. It will use the file INFILE as input and create a new file called OUTFILE as output. The job will have a time limit of 10 minutes and will run in job class A.

Summary: Empowering Mainframe Professionals

Mastering the art of creating control cards unlocks a world of possibilities in mainframe computing. By following these step-by-step instructions and understanding the underlying concepts, you can effectively manage jobs, optimize resource utilization, and streamline your mainframe operations.

Frequently Discussed Topics

1. What is the purpose of a job statement?

A job statement identifies the job and specifies its parameters, such as the job name, job class, and resource requirements.

2. How do I specify the execution command?

The execution command specifies the program or command to be executed. Use the EXEC PGM statement to define the program name and any parameters it requires.

3. What is the difference between SHR and NEW disposition?

SHR disposition allows multiple jobs to access the file simultaneously, while NEW disposition creates a new file and deletes any existing file with the same name.

4. What is the purpose of the /* statement?

The /* statement indicates the end of the control card and signals to the operating system that all job instructions have been provided.

5. How do I submit a control card?

Use the SUBMIT command to submit a control card to the operating system. The syntax is:

“`
SUBMIT jobname