ENABLE in COBOL

Learn about the ENABLE statement in COBOL, including its usage in communication handling, device activation, and system resource management.

Understanding ENABLE

The ENABLE statement is a crucial component in COBOL's communication handling capabilities. It activates communication endpoints and makes system resources available for use in your COBOL programs.

Key Characteristics

  • Activates communication endpoints
  • Manages system resources
  • Supports various device types
  • Handles connection establishment

Basic ENABLE Usage

Simple Device Activation

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       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       SOURCE-COMPUTER. IBM-370.
       OBJECT-COMPUTER. IBM-370.
       
       DATA DIVISION.
       COMMUNICATION SECTION.
       CD  COMM-PORT
           FOR INITIAL INPUT
           SYMBOLIC TERMINAL IS TERM-ID.
       
       PROCEDURE DIVISION.
           ENABLE INPUT TERMINAL COMM-PORT
           IF COMM-STATUS NOT = "0000"
               PERFORM HANDLE-ENABLE-ERROR
           END-IF

Multiple Device Activation

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       ENABLE INPUT TERMINAL COMM-PORT-1
               COMM-PORT-2
               COMM-PORT-3
       ON EXCEPTION
           PERFORM HANDLE-ENABLE-ERROR
       NOT ON EXCEPTION
           PERFORM ACTIVATION-SUCCESS

Error Handling

Comprehensive Error Management

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       WORKING-STORAGE SECTION.
       01  WS-STATUS-CODE    PIC X(4).
       01  WS-ERROR-MESSAGE  PIC X(50).
       
       PROCEDURE DIVISION.
           ENABLE INPUT TERMINAL COMM-PORT
               ON EXCEPTION
                   MOVE COMM-STATUS TO WS-STATUS-CODE
                   EVALUATE WS-STATUS-CODE
                       WHEN "0001"
                           MOVE "Device already enabled" 
                               TO WS-ERROR-MESSAGE
                       WHEN "0002"
                           MOVE "Device not available" 
                               TO WS-ERROR-MESSAGE
                       WHEN OTHER
                           MOVE "Unknown error" 
                               TO WS-ERROR-MESSAGE
                   END-EVALUATE
                   PERFORM LOG-ERROR
               NOT ON EXCEPTION
                   PERFORM NORMAL-PROCESSING
           END-ENABLE

Advanced ENABLE Features

Using ENABLE with advanced communication features:

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       SPECIAL-NAMES.
           CONSOLE IS CONSOLE-NAME
           TERMINAL IS TERM-NAME.
       
       PROCEDURE DIVISION.
           ENABLE INPUT TERMINAL COMM-PORT
               KEY IS SECURITY-KEY
               CONV-ID IS TRANSACTION-ID
           IF ENABLE-STATUS NOT = "0000"
               EVALUATE TRUE
                   WHEN SECURITY-ERROR
                       PERFORM HANDLE-SECURITY-VIOLATION
                   WHEN DEVICE-ERROR
                       PERFORM HANDLE-DEVICE-ERROR
                   WHEN OTHER
                       PERFORM HANDLE-UNKNOWN-ERROR
               END-EVALUATE
           END-IF

Resource Management

Lifecycle Management

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       WORKING-STORAGE SECTION.
       01  WS-RESOURCE-TABLE.
           05  WS-RESOURCE OCCURS 10 TIMES.
               10  WS-RESOURCE-ID    PIC X(8).
               10  WS-RESOURCE-STATE PIC X.
                   88  WS-RESOURCE-ENABLED  VALUE "E".
                   88  WS-RESOURCE-DISABLED VALUE "D".
       
       PROCEDURE DIVISION.
           PERFORM VARYING WS-IDX FROM 1 BY 1
                   UNTIL WS-IDX > 10
               IF WS-RESOURCE-DISABLED(WS-IDX)
                   ENABLE INPUT TERMINAL 
                       CORRESPONDING-PORT(WS-IDX)
                   IF ENABLE-SUCCESS
                       SET WS-RESOURCE-ENABLED(WS-IDX) 
                           TO TRUE
                   END-IF
               END-IF
           END-PERFORM

Best Practices

  • Always check status after ENABLE
  • Implement proper error handling
  • Maintain resource state tracking
  • Use appropriate timeouts
  • Document device requirements

Common ENABLE Patterns

Retry Logic

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       WORKING-STORAGE SECTION.
       01  WS-RETRY-COUNT   PIC 9(2) VALUE ZERO.
       01  WS-MAX-RETRIES   PIC 9(2) VALUE 3.
       
       PROCEDURE DIVISION.
           PERFORM UNTIL WS-RETRY-COUNT >= WS-MAX-RETRIES
               ENABLE INPUT TERMINAL COMM-PORT
               IF ENABLE-SUCCESS
                   PERFORM PROCESS-SUCCESS
                   EXIT PERFORM
               ELSE
                   ADD 1 TO WS-RETRY-COUNT
                   IF WS-RETRY-COUNT < WS-MAX-RETRIES
                       PERFORM WAIT-ROUTINE
                   END-IF
               END-IF
           END-PERFORM
           
           IF WS-RETRY-COUNT >= WS-MAX-RETRIES
               PERFORM HANDLE-FINAL-ERROR
           END-IF

Performance Considerations

  • Minimize enable/disable cycles
  • Use appropriate timeout values
  • Consider resource constraints
  • Monitor system load
  • Implement efficient error handling

Frequently Asked Questions

Related Pages

Related Concepts

Communication Handling

Understanding communication handling and device management in COBOL

Resource Management

Best practices for managing system resources in COBOL applications

Error Handling

Techniques for handling errors and exceptions in COBOL programs