What is GLOBAL in COBOL programming?

GLOBAL is a clause that makes data items or file names accessible to nested programs within a program hierarchy. It enables data sharing between main programs and their contained subprograms without passing parameters through the LINKAGE SECTION.

How do I use GLOBAL for data sharing?

Specify GLOBAL in the data item declaration: 01 SHARED-DATA GLOBAL PIC X(50). This makes the data item accessible to all nested programs within the containing program, enabling direct access without parameter passing.

What's the difference between GLOBAL and EXTERNAL data?

GLOBAL data is shared within a program hierarchy (main program and its nested subprograms), while EXTERNAL data is shared across separate, independently compiled programs. GLOBAL has hierarchical scope; EXTERNAL has application-wide scope.

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COBOL Tutorial

COBOL GLOBAL Clause

The GLOBAL clause represents a sophisticated data sharing mechanism within COBOL program hierarchies, serving as the primary specification for enabling data visibility and accessibility across nested program structures without requiring explicit parameter passing through linkage sections. This clause embodies the principles of hierarchical data management by providing controlled scope extension capabilities, enabling efficient inter-program communication patterns, and supporting modular programming architectures while maintaining data encapsulation boundaries and ensuring predictable variable access in enterprise applications that require structured program organization, shared data processing, and maintainable code architectures with clear data visibility rules.

Syntax and Usage

GLOBAL Clause Syntax

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01 data-name GLOBAL PIC clause.
01 data-name PIC clause GLOBAL.
 
FD file-name GLOBAL.
 
*> Examples:
01 SHARED-COUNTER GLOBAL PIC 9(5) VALUE 0.
01 COMMON-WORK-AREA GLOBAL.
   05 STATUS-FLAG PIC X.
   05 ERROR-MESSAGE PIC X(50).
 
FD SHARED-FILE GLOBAL.

Data Sharing

Program Hierarchy

Scope Management

Basic GLOBAL Examples

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IDENTIFICATION DIVISION.
PROGRAM-ID. MAIN-PROGRAM.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
*> Global data accessible to nested programs
01  GLOBAL-CONFIGURATION GLOBAL.
    05  APPLICATION-MODE    PIC X(10) VALUE 'PRODUCTION'.
    05  DEBUG-LEVEL         PIC 9 VALUE 1.
    05  MAX-RECORDS         PIC 9(7) VALUE 1000000.
 
01  SHARED-COUNTERS GLOBAL.
    05  TOTAL-PROCESSED     PIC 9(8) VALUE 0.
    05  ERROR-COUNT         PIC 9(5) VALUE 0.
    05  WARNING-COUNT       PIC 9(5) VALUE 0.
 
01  GLOBAL-WORK-AREA GLOBAL.
    05  CURRENT-OPERATION   PIC X(20).
    05  LAST-ERROR-MESSAGE  PIC X(80).
    05  PROCESSING-DATE     PIC 9(8).
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    MOVE FUNCTION CURRENT-DATE(1:8) TO PROCESSING-DATE
    MOVE 'INITIALIZATION' TO CURRENT-OPERATION
    
    DISPLAY 'Starting main processing...'
    CALL 'VALIDATION-MODULE'
    CALL 'PROCESSING-MODULE'
    CALL 'REPORTING-MODULE'
    
    DISPLAY 'Total processed: ' TOTAL-PROCESSED
    DISPLAY 'Errors: ' ERROR-COUNT
    DISPLAY 'Warnings: ' WARNING-COUNT
    STOP RUN.
 
*> Nested program with access to global data
IDENTIFICATION DIVISION.
PROGRAM-ID. VALIDATION-MODULE.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  WS-COUNTER              PIC 9(3).
 
PROCEDURE DIVISION.
VALIDATION-PROCESSING.
    MOVE 'DATA VALIDATION' TO CURRENT-OPERATION
    
    *> Access global counters and configuration
    IF DEBUG-LEVEL > 0
        DISPLAY 'Debug: Starting validation in ' APPLICATION-MODE ' mode'
    END-IF
    
    *> Simulate validation processing
    PERFORM VARYING WS-COUNTER FROM 1 BY 1 UNTIL WS-COUNTER > 100
        ADD 1 TO TOTAL-PROCESSED
        
        *> Simulate occasional errors
        IF FUNCTION MOD(WS-COUNTER, 25) = 0
            ADD 1 TO ERROR-COUNT
            MOVE 'Validation error in record processing' TO LAST-ERROR-MESSAGE
        END-IF
    END-PERFORM
    
    EXIT PROGRAM.
 
END PROGRAM VALIDATION-MODULE.
 
IDENTIFICATION DIVISION.
PROGRAM-ID. PROCESSING-MODULE.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  WS-COUNTER              PIC 9(3).
 
PROCEDURE DIVISION.
PROCESSING-LOGIC.
    MOVE 'RECORD PROCESSING' TO CURRENT-OPERATION
    
    *> Access and modify global data
    PERFORM VARYING WS-COUNTER FROM 1 BY 1 UNTIL WS-COUNTER > 200
        ADD 1 TO TOTAL-PROCESSED
        
        IF TOTAL-PROCESSED > MAX-RECORDS
            ADD 1 TO WARNING-COUNT
            MOVE 'Maximum record limit approaching' TO LAST-ERROR-MESSAGE
            EXIT PERFORM
        END-IF
    END-PERFORM
    
    EXIT PROGRAM.
 
END PROGRAM PROCESSING-MODULE.
 
IDENTIFICATION DIVISION.
PROGRAM-ID. REPORTING-MODULE.
 
PROCEDURE DIVISION.
REPORTING-LOGIC.
    MOVE 'REPORT GENERATION' TO CURRENT-OPERATION
    
    *> Generate summary report using global data
    DISPLAY 'Processing Summary Report'
    DISPLAY 'Date: ' PROCESSING-DATE
    DISPLAY 'Mode: ' APPLICATION-MODE
    DISPLAY 'Records Processed: ' TOTAL-PROCESSED
    DISPLAY 'Error Count: ' ERROR-COUNT
    DISPLAY 'Warning Count: ' WARNING-COUNT
    
    IF ERROR-COUNT > 0
        DISPLAY 'Last Error: ' LAST-ERROR-MESSAGE
    END-IF
    
    EXIT PROGRAM.
 
END PROGRAM REPORTING-MODULE.
 
END PROGRAM MAIN-PROGRAM.

Key Features and Benefits

Hierarchical Data Sharing

• Automatic data visibility
• No parameter passing required
• Simplified program interfaces
• Reduced linkage complexity

Modular Programming

• Nested program support
• Shared configuration data
• Common work areas
• Centralized state management

Interactive Tutorial

Hands-On Exercise: Shared Data Management

Practice using GLOBAL for effective data sharing in nested programs

Exercise 1: Configuration Management

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*> Main Program
01 SYSTEM-CONFIG GLOBAL.
   05 DATABASE-URL PIC X(50) VALUE 'DB.COMPANY.COM'.
   05 TIMEOUT-SECONDS PIC 9(3) VALUE 30.
   05 RETRY-COUNT PIC 9(2) VALUE 3.
   05 LOG-LEVEL PIC 9 VALUE 2.
 
*> Nested Program
IDENTIFICATION DIVISION.
PROGRAM-ID. DATABASE-MODULE.
 
PROCEDURE DIVISION.
    *> Access global configuration
    IF LOG-LEVEL > 1
        DISPLAY 'Connecting to: ' DATABASE-URL
        DISPLAY 'Timeout: ' TIMEOUT-SECONDS ' seconds'
    END-IF
    
    *> Use configuration values
    PERFORM DATABASE-CONNECT
    EXIT PROGRAM.

Exercise 2: Error Tracking

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*> Global error tracking structure
01 ERROR-TRACKING GLOBAL.
   05 ERROR-OCCURRED PIC X VALUE 'N'.
   05 ERROR-MODULE PIC X(20).
   05 ERROR-CODE PIC 9(4).
   05 ERROR-DESCRIPTION PIC X(100).
 
*> Nested program using error tracking
IDENTIFICATION DIVISION.
PROGRAM-ID. FILE-PROCESSOR.
 
PROCEDURE DIVISION.
    MOVE 'FILE-PROCESSOR' TO ERROR-MODULE
    
    *> Simulate error condition
    IF FILE-STATUS NOT = '00'
        MOVE 'Y' TO ERROR-OCCURRED
        MOVE 1001 TO ERROR-CODE
        MOVE 'File access error during processing' TO ERROR-DESCRIPTION
    END-IF.

Advanced GLOBAL Patterns

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IDENTIFICATION DIVISION.
PROGRAM-ID. ADVANCED-GLOBAL-DEMO.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
*> Global application state
01  APPLICATION-STATE GLOBAL.
    05  CURRENT-USER-ID     PIC X(10).
    05  SESSION-TOKEN       PIC X(32).
    05  TRANSACTION-ID      PIC 9(10).
    05  PROCESSING-STAGE    PIC 9(2) VALUE 1.
 
*> Global performance metrics
01  PERFORMANCE-METRICS GLOBAL.
    05  START-TIME          PIC 9(8).
    05  END-TIME            PIC 9(8).
    05  RECORDS-PER-SECOND  PIC 9(5)V99.
    05  MEMORY-USAGE        PIC 9(7).
 
*> Global business rules
01  BUSINESS-RULES GLOBAL.
    05  MIN-ORDER-AMOUNT    PIC 9(7)V99 VALUE 10.00.
    05  MAX-DISCOUNT-PCT    PIC 9(2)V99 VALUE 25.00.
    05  TAX-RATE            PIC 9V9999 VALUE 0.0825.
    05  SHIPPING-THRESHOLD  PIC 9(5)V99 VALUE 100.00.
 
*> Global audit trail
01  AUDIT-TRAIL GLOBAL.
    05  AUDIT-ENTRIES OCCURS 100 TIMES.
        10  AUDIT-TIMESTAMP PIC 9(14).
        10  AUDIT-USER      PIC X(10).
        10  AUDIT-ACTION    PIC X(20).
        10  AUDIT-DETAILS   PIC X(100).
    05  AUDIT-COUNTER       PIC 9(3) VALUE 0.
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    MOVE 'USER001' TO CURRENT-USER-ID
    MOVE FUNCTION CURRENT-DATE(9:6) TO START-TIME
    MOVE 1001 TO TRANSACTION-ID
    
    CALL 'AUTHENTICATION-MODULE'
    CALL 'ORDER-PROCESSING-MODULE'
    CALL 'AUDIT-MODULE'
    
    STOP RUN.
 
*> Authentication module with global state access
IDENTIFICATION DIVISION.
PROGRAM-ID. AUTHENTICATION-MODULE.
 
PROCEDURE DIVISION.
AUTHENTICATION-LOGIC.
    MOVE 'AUTHENTICATION' TO AUDIT-ACTION
    ADD 1 TO AUDIT-COUNTER
    MOVE FUNCTION CURRENT-DATE TO AUDIT-TIMESTAMP(AUDIT-COUNTER)
    MOVE CURRENT-USER-ID TO AUDIT-USER(AUDIT-COUNTER)
    MOVE 'User authentication successful' TO AUDIT-DETAILS(AUDIT-COUNTER)
    
    *> Generate session token
    STRING 'TOKEN' DELIMITED BY SIZE
           CURRENT-USER-ID DELIMITED BY SPACE
           TRANSACTION-ID DELIMITED BY SIZE
           INTO SESSION-TOKEN
    
    MOVE 2 TO PROCESSING-STAGE
    EXIT PROGRAM.
 
END PROGRAM AUTHENTICATION-MODULE.
 
*> Order processing with business rules
IDENTIFICATION DIVISION.
PROGRAM-ID. ORDER-PROCESSING-MODULE.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  ORDER-DATA.
    05  ORDER-AMOUNT        PIC 9(7)V99.
    05  DISCOUNT-AMOUNT     PIC 9(5)V99.
    05  TAX-AMOUNT          PIC 9(5)V99.
    05  SHIPPING-AMOUNT     PIC 9(3)V99.
    05  TOTAL-AMOUNT        PIC 9(8)V99.
 
PROCEDURE DIVISION.
ORDER-PROCESSING-LOGIC.
    MOVE 'ORDER-PROCESSING' TO AUDIT-ACTION
    ADD 1 TO AUDIT-COUNTER
    MOVE FUNCTION CURRENT-DATE TO AUDIT-TIMESTAMP(AUDIT-COUNTER)
    MOVE CURRENT-USER-ID TO AUDIT-USER(AUDIT-COUNTER)
    
    *> Apply business rules using global data
    IF ORDER-AMOUNT < MIN-ORDER-AMOUNT
        MOVE 'Order below minimum amount' TO AUDIT-DETAILS(AUDIT-COUNTER)
        EXIT PROGRAM
    END-IF
    
    *> Calculate tax using global rate
    MULTIPLY ORDER-AMOUNT BY TAX-RATE GIVING TAX-AMOUNT
    
    *> Apply shipping rules
    IF ORDER-AMOUNT >= SHIPPING-THRESHOLD
        MOVE 0 TO SHIPPING-AMOUNT
    ELSE
        MOVE 9.99 TO SHIPPING-AMOUNT
    END-IF
    
    ADD ORDER-AMOUNT TAX-AMOUNT SHIPPING-AMOUNT GIVING TOTAL-AMOUNT
    MOVE 'Order processed successfully' TO AUDIT-DETAILS(AUDIT-COUNTER)
    
    MOVE 3 TO PROCESSING-STAGE
    EXIT PROGRAM.
 
END PROGRAM ORDER-PROCESSING-MODULE.
 
*> Audit module for logging
IDENTIFICATION DIVISION.
PROGRAM-ID. AUDIT-MODULE.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  WS-INDEX                PIC 9(3).
 
PROCEDURE DIVISION.
AUDIT-PROCESSING.
    MOVE FUNCTION CURRENT-DATE(9:6) TO END-TIME
    
    DISPLAY 'Audit Trail Summary:'
    DISPLAY 'Transaction ID: ' TRANSACTION-ID
    DISPLAY 'User: ' CURRENT-USER-ID
    DISPLAY 'Processing Stage: ' PROCESSING-STAGE
    DISPLAY 'Start Time: ' START-TIME
    DISPLAY 'End Time: ' END-TIME
    
    DISPLAY 'Audit Entries:'
    PERFORM VARYING WS-INDEX FROM 1 BY 1 UNTIL WS-INDEX > AUDIT-COUNTER
        DISPLAY WS-INDEX ': ' AUDIT-TIMESTAMP(WS-INDEX) ' - '
                AUDIT-ACTION(WS-INDEX) ' - ' AUDIT-DETAILS(WS-INDEX)
    END-PERFORM
    
    EXIT PROGRAM.
 
END PROGRAM AUDIT-MODULE.
 
END PROGRAM ADVANCED-GLOBAL-DEMO.

Best Practices

Knowledge Check

Test Your Understanding

Question 1: Basic Usage

How do you declare a global data item in COBOL?

Answer: 01 data-name GLOBAL PIC clause. or 01 data-name PIC clause GLOBAL.

Question 2: Scope Rules

Which programs can access GLOBAL data items?

Answer: All nested programs within the program hierarchy where the GLOBAL data is declared can access it directly without parameter passing.

Question 3: Best Practice

When should you use GLOBAL data instead of parameter passing?

Answer: Use GLOBAL for configuration data, shared state, and data that multiple nested programs need to access. Avoid for simple parameter passing or when data encapsulation is important.

Common Patterns

Configuration Sharing

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01 APP-CONFIG GLOBAL.
   05 DATABASE-NAME PIC X(20).
   05 MAX-CONNECTIONS PIC 9(3).
   05 TIMEOUT-VALUE PIC 9(5).
   05 DEBUG-MODE PIC X VALUE 'N'.
 
*> All nested programs can access
*> configuration without parameters

State Management

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01 PROCESS-STATE GLOBAL.
   05 CURRENT-STEP PIC 9(2).
   05 ERROR-FLAG PIC X VALUE 'N'.
   05 RECORDS-PROCESSED PIC 9(8).
   05 LAST-OPERATION PIC X(20).
 
*> Shared state across all modules

COBOL Tutorial

COBOL GLOBAL Clause

Syntax and Usage

Basic GLOBAL Examples

Key Features and Benefits

Interactive Tutorial

Exercise 1: Configuration Management

Exercise 2: Error Tracking

Advanced GLOBAL Patterns

Best Practices

Knowledge Check

Question 1: Basic Usage

Question 2: Scope Rules

Question 3: Best Practice

Common Patterns

Frequently Asked Questions

Related Concepts

Data Sharing

Program Structure

Variable Scope

Related Pages

COBOL Tutorial

COBOL GLOBAL Clause

Syntax and Usage

Basic GLOBAL Examples

Key Features and Benefits

Interactive Tutorial

Exercise 1: Configuration Management

Exercise 2: Error Tracking

Advanced GLOBAL Patterns

Best Practices

Global Data Design

Scope Management

Maintenance Considerations

Knowledge Check

Question 1: Basic Usage

Question 2: Scope Rules

Question 3: Best Practice

Common Patterns

Frequently Asked Questions

Can GLOBAL data be modified by nested programs?

What happens to GLOBAL data when a nested program ends?

Can I use GLOBAL with file descriptions?

How does GLOBAL differ from COMMON in other languages?

Related Concepts

Data Sharing

Program Structure

Variable Scope

Related Pages