What is SORTJOIN in Mainframe?

Introduction on SORTJOIN

In the world of mainframe computing, JCL (Job Control Language) plays a crucial role in defining and managing batch jobs. One of the fundamental tasks in data processing is sorting, and JCL offers several powerful sorting techniques. Among these techniques, SORTJOIN stands out as an efficient method for merging and sorting data sets based on specified key fields. In this blog post, we will delve into the details of SORTJOIN in JCL, exploring its features, benefits, and usage.


SORTJOIN is a JCL utility used for sorting and merging two or more input files based on specified key fields. It performs a sort operation on the input files and merges them into a single output file. This utility is particularly useful when dealing with large volumes of data, as it ensures efficient and accurate sorting.

What is SORTJOIN in Mainframe?

Key Features of SORTJOIN:

  1. Sorting and Merging: SORTJOIN combines the functionalities of sorting and merging data sets into a single step. It allows you to sort the input files individually and merge them based on common key fields.
  2. Key Field Definition: SORTJOIN supports the definition of one or more key fields within the input files. These key fields determine the sorting order and are crucial for the merge operation.
  3. Record Layout Preservation: SORTJOIN preserves the original record layout of the input files during the sort and merge process. This ensures that the output file maintains the same structure as the input files.
  4. Versatile Sorting Options: SORTJOIN offers various sorting options, such as ascending or descending order, numerical or alphanumeric sorting, and ignoring leading or trailing blanks. These options provide flexibility in tailoring the sorting behavior to suit specific requirements.
  5. Join Functions: SORTJOIN allows the use of join functions, such as INNER JOIN, LEFT JOIN, and RIGHT JOIN, to specify how the merging should be performed. These functions help combine data from multiple files based on matching key values.

Benefits of Using SORTJOIN

  1. Efficiency: SORTJOIN is designed to handle large volumes of data efficiently. It utilizes sorting algorithms optimized for performance, ensuring that the sorting and merging operations are executed as quickly as possible.
  2. Accuracy: SORTJOIN guarantees accurate sorting and merging of data sets. It eliminates the need for manual interventions, reducing the risk of errors that may occur during manual sorting and merging processes.
  3. Scalability: SORTJOIN is highly scalable, allowing it to handle datasets of various sizes. Whether you are dealing with small or large files, SORTJOIN can effectively sort and merge them, delivering consistent results.

Usage of SORTJOIN in JCL: To use SORTJOIN in JCL, you need to define the input files, specify the key fields, and configure any additional options as required.

Here is a sample JCL code snippet showcasing the usage of SORTJOIN:





// SPACE=(CYL,(10,10),RLSE),










In the above example, two input files (INPUT1 and INPUT2) are sorted individually based on the first 10 characters (key field) using the SORT statement. The sorted files are then merged using the JOINKEYS and REFORMAT statements, combining the matching records based on the key field. The output is written to the OUTPUT file.

Limitations of SORTJOIN

While SORTJOIN is a powerful utility in JCL for sorting and merging data sets, it does have some limitations. It’s important to be aware of these limitations to ensure that SORTJOIN is used appropriately in your data processing tasks. Here are some limitations of SORTJOIN:

  • Memory Constraints: SORTJOIN requires a significant amount of memory to perform the sorting and merging operations efficiently. If the available memory is insufficient to handle the size of the input files, it can lead to performance issues or even job failures. Careful consideration should be given to memory allocation and the size of the datasets being processed.
  • Key Field Length: SORTJOIN requires the key fields used for sorting and merging to have a fixed length. If the key fields in the input files have varying lengths or if the key fields are not in a fixed position within the records, additional preprocessing steps may be necessary to ensure compatibility with SORTJOIN.
  • Single-Key Sorting: SORTJOIN supports sorting and merging based on a single key field. If you need to sort and merge data based on multiple key fields or complex sorting criteria, additional programming logic or alternative sorting techniques may be required.
  • Performance Impact with Large Datasets: While SORTJOIN is designed to handle large volumes of data efficiently, extremely large datasets can still pose challenges. Processing very large files may result in longer execution times, increased memory requirements, and potential performance bottlenecks. It is essential to assess the size and complexity of your data before employing SORTJOIN.
  • Disk Space Requirements: The output file generated by SORTJOIN may consume a considerable amount of disk space, especially when merging large input files. Adequate disk space allocation and management should be considered to ensure the availability of sufficient storage resources.
  • Limited Error Handling: SORTJOIN has limited built-in error handling capabilities. If any errors occur during the sorting or merging process, they need to be captured and handled through appropriate JCL or programming logic. Proper error handling mechanisms should be implemented to address any potential issues that may arise.
  • Sequential Processing: SORTJOIN operates in a sequential manner, processing one record at a time. This means that it may not be the most suitable option for scenarios that require parallel processing or real-time data merging.
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While SORTJOIN offers significant advantages in many sorting and merging scenarios, it is essential to consider these limitations and evaluate whether they align with your specific requirements. Depending on the complexity of your data and the processing needs, you may need to explore alternative sorting techniques or combine SORTJOIN with other utilities to achieve optimal results.

Final Thoughts on SORTJOIN

SORTJOIN is a powerful utility in JCL that enables efficient sorting and merging of data sets based on specified key fields. Its ability to handle large volumes of data, flexibility in sorting options, and support for join functions make it an indispensable tool for data processing in mainframe environments. By understanding the features, benefits, and usage of SORTJOIN, you can enhance your data processing capabilities and streamline your batch job workflows.

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