Fixed Format

Enhanced Definition

In the context of IBM z/OS, "Fixed Format" primarily refers to data records or source code where each record or line has a predefined, unchanging length and structure. For data, this means every record occupies the exact same number of bytes, facilitating predictable access and processing. For source code, it dictates specific column assignments for different elements.

Key Characteristics

- Consistent Record Length: All records within a fixed-format dataset have an identical logical record length (LRECL), which is defined at the time of dataset allocation.
- Predictable Structure: The layout of data fields within each record is uniform across all records, allowing programs to access data elements at fixed offsets.
- Efficient Processing: Due to the consistent record size, the system can efficiently read and write records without needing to parse length indicators, often leading to faster I/O operations compared to variable-format records.
- Defined by RECFM=F or RECFM=FB: In JCL DD statements, RECFM=F (Fixed) or RECFM=FB (