In JCL, referencing data sets is a crucial aspect of managing and manipulating data. This topic will cover how to reference existing data sets, the syntax involved, and practical examples to help you understand the process.

1. Data Set Naming Conventions: Understanding the rules for naming data sets.
2. Referencing Existing Data Sets: How to reference data sets that already exist.
3. Using the DSN Parameter: Detailed explanation of the DSN (Data Set Name) parameter.
4. Referencing Temporary Data Sets: How to reference data sets created within the same job.

Before referencing data sets, it's important to understand the naming conventions:

• Qualified Names: Data set names are typically qualified, meaning they are divided into segments separated by periods (e.g., USER.DATA.SET).
• Maximum Length: The maximum length of a data set name is 44 characters.
• Characters: Names can include alphanumeric characters and special characters like @, #, and $.

To reference an existing data set in JCL, you use the DSN parameter within a DD statement. The DSN parameter specifies the name of the data set you want to use.

• DDNAME: The name you assign to the DD statement.
• DSN: The data set name.
• DISP: The disposition parameter, which specifies the status of the data set (e.g., SHR for shared access).

In this example:

• INPUT1 references an existing data set USER.DATA.INPUT with shared access.
• OUTPUT1 references an existing data set USER.DATA.OUTPUT with exclusive access (indicated by DISP=OLD).

The DSN parameter is used to specify the name of the data set. It can be used in various ways depending on the context:

• Fully Qualified Name: Specifies the complete name of the data set.
• Partially Qualified Name: Uses a portion of the name, often with symbolic parameters.

In this example, &USER is a symbolic parameter that will be replaced with a specific value at runtime.

Temporary data sets are created and used within the same job. They are typically referenced using special naming conventions.

• &&TEMPDS: Indicates a temporary data set.
• DISP=(NEW,PASS): Specifies that the data set is new and will be passed to subsequent steps.

In this example:

• STEP1 creates a temporary data set &&TEMPDS.
• STEP2 references the temporary data set &&TEMPDS created in STEP1.

Write a JCL job that references an existing data set for input and creates a temporary data set for output, which is then used in a subsequent step.

• STEP1:
  • INPUT references an existing data set USER.DATA.INPUT with shared access.
  • TEMPDS creates a new temporary data set &&TEMPDS.
• STEP2:
  • OUTPUT references the temporary data set &&TEMPDS created in STEP1.

• Incorrect Data Set Names: Ensure that data set names follow the naming conventions and do not exceed 44 characters.
• Disposition Errors: Use the correct disposition parameters (DISP) to avoid conflicts and ensure proper data set handling.
• Temporary Data Set References: When referencing temporary data sets, ensure that the naming and disposition parameters are consistent across steps.

Referencing data sets in JCL is a fundamental skill that allows you to manage and manipulate data effectively. By understanding the syntax and conventions, you can confidently reference both existing and temporary data sets in your JCL jobs. Practice with the provided examples and exercises to reinforce your understanding and prepare for more advanced topics.