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ASA - American Standards Association

Enhanced Definition

In the context of IBM mainframes and z/OS, ASA refers to the **American Standards Association (ASA) control characters** standard, a set of single-character codes used at the beginning of print records to control vertical spacing and page breaks on line printers. It dictates how a printer should advance paper before or after printing a line.

Key Characteristics

- Single-Character Prefix: Each print record (logical line) begins with a single control character that is not printed but interpreted by the printer or spool system.
- Standardized Actions: Specific characters ( , 0, -, +, 1) correspond to predefined actions like single spacing, double spacing, triple spacing, overprinting, and new page.
- Legacy Standard: Primarily developed for impact line printers, it remains widely used for batch report generation on z/OS.
- JCL Integration: Its usage is typically specified in JCL DCB (Data Control Block) parameters, commonly RECFM=FBA (Fixed Block with ASA) or VBA (Variable Block with ASA).
- Programmatic Control: Application programs, especially those written in COBOL, generate these control characters as the first byte of each output record.

Use Cases

- Batch Report Formatting: Generating formatted reports from batch jobs where specific line spacing and page breaks are required for readability.
- SYSOUT Datasets: Directing output to SYSOUT datasets, which are then processed by the Job Entry Subsystem (JES) for printing, often with ASA control characters embedded.
- COBOL WRITE Statements: Utilizing WRITE statements with AFTER ADVANCING or BEFORE ADVANCING clauses to implicitly or explicitly insert ASA control characters.
- Archiving and Viewing: When SYSOUT is archived or viewed electronically, the ASA control characters must be interpreted by the viewing software to render the report correctly.

Related Concepts

ASA control characters are intrinsically linked to JCL through the DCB parameter RECFM (Record Format), which specifies if a dataset contains ASA characters. COBOL programs frequently generate these characters using WRITE statements to format output destined for line printers or SYSOUT datasets. The Job Entry Subsystem (JES) processes SYSOUT datasets and interprets ASA characters to control physical or virtual printer output.

Best Practices:

Consistent RECFM Specification: Ensure that the RECFM in the JCL DD statement (e.g., RECFM=FBA) matches the program's expectation and generation of ASA control characters.
Explicit COBOL ADVANCING: Use AFTER ADVANCING or BEFORE ADVANCING clauses in COBOL WRITE statements to clearly indicate vertical spacing, rather than relying on default behaviors.
Avoid Overprinting (+): While + allows overprinting, it can lead to unpredictable results or be ignored by modern print drivers and PDF converters; use with caution or avoid if possible.
Test Print Output: Always verify the actual printed or rendered output to ensure that ASA control characters are being interpreted correctly and the formatting is as intended.
Modernization Considerations: When migrating or modernizing applications, consider converting ASA-controlled reports to formats like PDF or PCL that offer more robust and device-independent formatting capabilities.