Detail Record

Enhanced Definition

A `detail record` typically represents an individual transaction, event, or specific piece of information within a dataset or file, often used as input for batch processing or for generating report lines. It contains granular data that contributes to a larger process or summary, reflecting a single occurrence or entity.

Key Characteristics

- Granularity: Contains specific, individual data points for a single entity or event (e.g., a single customer transaction, an employee's time entry, a stock movement).
- Input for Processing: Frequently serves as input to batch programs (e.g., COBOL programs) that update master files, perform calculations, or generate reports.
- Fixed or Variable Length: Can be structured as fixed-length records (common in older COBOL applications) or variable-length records, depending on the data and file organization.
- Sequential Access: Often stored in sequential datasets (e.g., PS or PDS members acting as sequential files) and processed sequentially by batch jobs.
- High Volume: Typically, there are many detail records in a file, reflecting numerous individual occurrences that need to be processed.

Use Cases

- Transaction Processing: A file of daily sales detail records is processed against an inventory master file to update stock levels and generate customer invoices.
- Report Generation: Each detail record from an input file (e.g., employee time entries) is read and formatted by a COBOL program to produce a single line on a payroll report.
- Audit Trails: Individual system events or user actions are captured as detail records in a log file for auditing, security analysis, and historical tracking.
- Data Transformation: Detail records from a legacy system are read, transformed according to new business rules, and written as new detail records to be consumed by a modern application.

Related Concepts

Detail records are fundamental to batch processing on z/OS, often interacting with master files where they drive updates or queries. They are typically processed by COBOL programs defined in JCL, which read and write these records using DD statements that specify the dataset. In reporting, detail records are the building blocks for report lines, which are then often aggregated into summary records or sections to provide higher-level insights.

Best Practices:

Data Validation: Implement robust validation routines within COBOL programs to ensure the integrity and correctness of detail record data upon input, preventing erroneous updates or reports.
Error Handling: Design programs to gracefully handle invalid or erroneous detail records, perhaps by writing them to an error file for later review and correction, rather than aborting the job.
Record Layout Documentation: Maintain clear and current documentation (e.g., COBOL COPYBOOKs) for the layout and fields within detail records to ensure consistency and interoperability across applications.
Efficient I/O: Optimize JCL and program logic for efficient reading and writing of detail records, especially for large volumes, using appropriate block sizes (BLKSIZE) and access methods.
Archiving: Establish policies for archiving or purging detail record files after they have served their purpose (e.g., after master file updates or report generation) to manage storage and compliance.