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COBOL Tutorial

COBOL USER-DEFAULT - Quick Reference

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Overview

USER-DEFAULT refers to per-user preferences and default values that personalize behavior. They typically override SYSTEM-DEFAULT values and are validated before use.

Common Sources

  • Environment variables or job parameters
  • Parameter files or VSAM datasets per user
  • Database tables keyed by user ID

Patterns and Usage

Layered Defaults

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* Load system default, overlay with user default
       01  SYS-DEFAULT-BUFFER   PIC 9(5) VALUE 4096.
       01  USER-DEFAULT-BUFFER  PIC 9(5) VALUE 0.
       01  EFFECTIVE-BUFFER     PIC 9(5).
       
       IF USER-DEFAULT-BUFFER NOT = 0
           MOVE USER-DEFAULT-BUFFER TO EFFECTIVE-BUFFER
       ELSE
           MOVE SYS-DEFAULT-BUFFER  TO EFFECTIVE-BUFFER
       END-IF

Validate ranges and apply business rules when merging defaults.

Fetching Defaults

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* Illustrative: fetching defaults (data source specific)
       * ENV or DB calls would be compiler/platform specific and are omitted here
       PERFORM LOAD-SYSTEM-DEFAULTS
       PERFORM LOAD-USER-DEFAULTS
       PERFORM MERGE-DEFAULTS

Best Practices

  • Validation - Constrain user values to safe ranges
  • Observability - Log default sources and applied values
  • Reset options - Provide a way to reset to system defaults

USER-DEFAULT Quick Reference

AspectDescriptionExample
LayeringUser overrides systemEffective = User if present
SourcesENV, files, DBVSAM profile by user
ValidationRange/format checksReject out-of-range

Test Your Knowledge

1. What does USER-DEFAULT generally mean in application design?

  • System-wide fallback values
  • User-specific defaults/preferences overriding system defaults
  • Compiler default values
  • File block sizes

2. Where are USER-DEFAULT values commonly sourced?

  • Hard-coded in source only
  • Environment variables, parameter files, database tables, or profile datasets
  • Only from JCL
  • Nowhere; they are not used

3. What is a best practice for USER-DEFAULT handling?

  • Fail if user default missing
  • Layer defaults: user overrides system, with safe fallbacks
  • Never persist defaults
  • Store defaults in program text

4. How do USER-DEFAULTs improve UX?

  • By forcing the same settings for everyone
  • By remembering per-user preferences to reduce repetitive input
  • By disabling configuration entirely
  • They do not improve UX

5. Which is appropriate for critical settings?

  • Trust user defaults without validation
  • Validate and constrain user defaults; provide sensible system defaults
  • Ignore user defaults
  • Disable logging

Frequently Asked Questions

Related Concepts

SYSTEM-DEFAULT

System-wide defaults and fallbacks.

Configuration

Managing configuration values.

Environment

Environment-driven behavior.

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