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COBOL Tutorial

COBOL STATUS Clause - Quick Reference

The STATUS clause in COBOL is used to specify a file status field that will contain status codes indicating the result of file operations. It provides a standardized way to handle file operation errors and determine program flow based on operation results.

Primary Use

Specify file status fields for error handling

Division

DATA DIVISION

Section

FILE SECTION

Status

Optional clause

Overview

The STATUS clause is part of the file description entry (FD) in the FILE SECTION of the DATA DIVISION. It allows you to specify a field that will contain status codes after file operations. These status codes provide information about whether the operation was successful or what type of error occurred. This is essential for proper error handling and program flow control in COBOL applications.

Syntax

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DATA DIVISION.
FILE SECTION.
FD  file-name
    [RECORD IS STANDARD]
    [BLOCK CONTAINS integer RECORDS]
    [RECORDING MODE IS mode]
    [LABEL RECORDS ARE STANDARD]
    [VALUE OF file-id IS literal]
    [STATUS field-name].
 
* Examples:
FD  CUSTOMER-FILE
    RECORD IS STANDARD
    BLOCK CONTAINS 10 RECORDS
    RECORDING MODE IS F
    LABEL RECORDS ARE STANDARD
    STATUS WS-CUSTOMER-STATUS.
 
FD  INVENTORY-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-INVENTORY-STATUS.

Practical Examples

Basic STATUS Usage

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* Basic STATUS clause example
IDENTIFICATION DIVISION.
PROGRAM-ID. STATUS-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
           ORGANIZATION IS SEQUENTIAL
           ACCESS MODE IS SEQUENTIAL
           FILE STATUS IS WS-CUSTOMER-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-CUSTOMER-STATUS.
 
01  CUSTOMER-RECORD.
    05  CUST-ID           PIC 9(5).
    05  CUST-NAME         PIC X(30).
    05  CUST-BALANCE      PIC 9(7)V99.
 
WORKING-STORAGE SECTION.
01  WS-CUSTOMER-STATUS    PIC X(2).
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    OPEN INPUT CUSTOMER-FILE
    
    * Check if file opened successfully
    IF WS-CUSTOMER-STATUS = "00"
        DISPLAY "File opened successfully"
        PERFORM READ-CUSTOMERS
        CLOSE CUSTOMER-FILE
    ELSE
        DISPLAY "Error opening file: " WS-CUSTOMER-STATUS
    END-IF
    
    STOP RUN.
 
READ-CUSTOMERS.
    READ CUSTOMER-FILE
        AT END
            DISPLAY "End of file reached"
        NOT AT END
            * Check if read was successful
            IF WS-CUSTOMER-STATUS = "00"
                DISPLAY "Customer: " CUST-ID " - " CUST-NAME
            ELSE
                DISPLAY "Error reading record: " WS-CUSTOMER-STATUS
            END-IF
    END-READ.

Explanation: This example demonstrates basic usage of the STATUS clause. The program defines a file with a status field (WS-CUSTOMER-STATUS) and checks the status after each file operation. The status code "00" indicates success, while other codes indicate various error conditions. This allows the program to handle errors gracefully and provide appropriate feedback to the user.

Error Handling with STATUS

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* STATUS clause with comprehensive error handling
IDENTIFICATION DIVISION.
PROGRAM-ID. STATUS-ERROR-HANDLING.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INVENTORY-FILE ASSIGN TO "INVENTORY.DAT"
           ORGANIZATION IS INDEXED
           ACCESS MODE IS RANDOM
           RECORD KEY IS INV-ITEM-ID
           FILE STATUS IS WS-INVENTORY-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  INVENTORY-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-INVENTORY-STATUS.
 
01  INVENTORY-RECORD.
    05  INV-ITEM-ID       PIC 9(5).
    05  INV-DESCRIPTION   PIC X(40).
    05  INV-QUANTITY      PIC 9(4).
    05  INV-PRICE         PIC 9(5)V99.
 
WORKING-STORAGE SECTION.
01  WS-INVENTORY-STATUS   PIC X(2).
01  WS-ERROR-MESSAGE      PIC X(50).
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    OPEN I-O INVENTORY-FILE
    PERFORM CHECK-FILE-STATUS "OPEN"
    
    * Try to read a specific record
    MOVE 12345 TO INV-ITEM-ID
    READ INVENTORY-FILE
    PERFORM CHECK-FILE-STATUS "READ"
    
    * Try to write a new record
    MOVE 99999 TO INV-ITEM-ID
    MOVE "NEW ITEM" TO INV-DESCRIPTION
    MOVE 100 TO INV-QUANTITY
    MOVE 25.50 TO INV-PRICE
    WRITE INVENTORY-RECORD
    PERFORM CHECK-FILE-STATUS "WRITE"
    
    CLOSE INVENTORY-FILE
    PERFORM CHECK-FILE-STATUS "CLOSE"
    
    STOP RUN.
 
CHECK-FILE-STATUS.
    USING OPERATION-TYPE.
    
    EVALUATE WS-INVENTORY-STATUS
        WHEN "00"
            DISPLAY OPERATION-TYPE " operation successful"
        WHEN "10"
            DISPLAY "End of file reached during " OPERATION-TYPE
        WHEN "23"
            DISPLAY "Record not found during " OPERATION-TYPE
        WHEN "30"
            DISPLAY "Permanent error during " OPERATION-TYPE
        WHEN "35"
            DISPLAY "File not found during " OPERATION-TYPE
        WHEN "37"
            DISPLAY "File access denied during " OPERATION-TYPE
        WHEN "39"
            DISPLAY "File already exists during " OPERATION-TYPE
        WHEN "41"
            DISPLAY "File already open during " OPERATION-TYPE
        WHEN OTHER
            DISPLAY "Unknown status " WS-INVENTORY-STATUS " during " OPERATION-TYPE
    END-EVALUATE.

Explanation: This example shows comprehensive error handling using the STATUS clause. The program defines a subroutine (CHECK-FILE-STATUS) that evaluates different status codes and provides specific error messages for each condition. This approach allows for detailed error reporting and helps in debugging file operation issues. The EVALUATE statement makes the code more readable and maintainable compared to multiple IF statements.

Multiple Files with STATUS

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* STATUS clause with multiple files
IDENTIFICATION DIVISION.
PROGRAM-ID. MULTIPLE-FILES-STATUS.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INPUT-FILE ASSIGN TO "INPUT.DAT"
           ORGANIZATION IS SEQUENTIAL
           ACCESS MODE IS SEQUENTIAL
           FILE STATUS IS WS-INPUT-STATUS.
           
    SELECT OUTPUT-FILE ASSIGN TO "OUTPUT.DAT"
           ORGANIZATION IS SEQUENTIAL
           ACCESS MODE IS SEQUENTIAL
           FILE STATUS IS WS-OUTPUT-STATUS.
           
    SELECT ERROR-FILE ASSIGN TO "ERROR.DAT"
           ORGANIZATION IS SEQUENTIAL
           ACCESS MODE IS SEQUENTIAL
           FILE STATUS IS WS-ERROR-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  INPUT-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-INPUT-STATUS.
 
01  INPUT-RECORD.
    05  INPUT-ID          PIC 9(5).
    05  INPUT-DATA        PIC X(50).
 
FD  OUTPUT-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-OUTPUT-STATUS.
 
01  OUTPUT-RECORD.
    05  OUTPUT-ID         PIC 9(5).
    05  OUTPUT-DATA       PIC X(50).
 
FD  ERROR-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-ERROR-STATUS.
 
01  ERROR-RECORD.
    05  ERROR-ID          PIC 9(5).
    05  ERROR-MESSAGE     PIC X(50).
 
WORKING-STORAGE SECTION.
01  WS-INPUT-STATUS       PIC X(2).
01  WS-OUTPUT-STATUS      PIC X(2).
01  WS-ERROR-STATUS       PIC X(2).
01  WS-EOF-FLAG           PIC X VALUE 'N'.
    88  END-OF-FILE       VALUE 'Y'.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    * Open all files
    OPEN INPUT INPUT-FILE
    IF WS-INPUT-STATUS NOT = "00"
        DISPLAY "Error opening input file: " WS-INPUT-STATUS
        STOP RUN
    END-IF
    
    OPEN OUTPUT OUTPUT-FILE
    IF WS-OUTPUT-STATUS NOT = "00"
        DISPLAY "Error opening output file: " WS-OUTPUT-STATUS
        CLOSE INPUT-FILE
        STOP RUN
    END-IF
    
    OPEN OUTPUT ERROR-FILE
    IF WS-ERROR-STATUS NOT = "00"
        DISPLAY "Error opening error file: " WS-ERROR-STATUS
        CLOSE INPUT-FILE OUTPUT-FILE
        STOP RUN
    END-IF
    
    * Process records
    PERFORM UNTIL END-OF-FILE
        READ INPUT-FILE
            AT END
                SET END-OF-FILE TO TRUE
            NOT AT END
                IF WS-INPUT-STATUS = "00"
                    PERFORM PROCESS-RECORD
                ELSE
                    PERFORM LOG-ERROR
                END-IF
        END-READ
    END-PERFORM
    
    * Close all files
    CLOSE INPUT-FILE OUTPUT-FILE ERROR-FILE
    STOP RUN.
 
PROCESS-RECORD.
    * Validate input record
    IF INPUT-ID > 0 AND INPUT-DATA NOT = SPACES
        MOVE INPUT-ID TO OUTPUT-ID
        MOVE INPUT-DATA TO OUTPUT-DATA
        WRITE OUTPUT-RECORD
        IF WS-OUTPUT-STATUS NOT = "00"
            PERFORM LOG-ERROR
        END-IF
    ELSE
        PERFORM LOG-ERROR
    END-IF.
 
LOG-ERROR.
    MOVE INPUT-ID TO ERROR-ID
    MOVE "Invalid record or write error" TO ERROR-MESSAGE
    WRITE ERROR-RECORD
    IF WS-ERROR-STATUS NOT = "00"
        DISPLAY "Error writing to error file: " WS-ERROR-STATUS
    END-IF.

Explanation: This example demonstrates using STATUS clauses with multiple files. Each file has its own status field, allowing the program to track the status of operations on each file independently. The program opens all files and checks their status before proceeding. If any file fails to open, the program closes previously opened files and stops. During processing, the program checks the status after each operation and logs errors to a separate error file. This approach ensures robust error handling across multiple file operations.

Status Code Validation

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* STATUS clause with status code validation
IDENTIFICATION DIVISION.
PROGRAM-ID. STATUS-VALIDATION.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT MASTER-FILE ASSIGN TO "MASTER.DAT"
           ORGANIZATION IS INDEXED
           ACCESS MODE IS DYNAMIC
           RECORD KEY IS MST-KEY
           ALTERNATE RECORD KEY IS MST-ALT-KEY
           FILE STATUS IS WS-MASTER-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  MASTER-FILE
    RECORD IS STANDARD
    RECORDING MODE IS F
    STATUS WS-MASTER-STATUS.
 
01  MASTER-RECORD.
    05  MST-KEY           PIC 9(5).
    05  MST-ALT-KEY       PIC X(10).
    05  MST-DATA          PIC X(100).
 
WORKING-STORAGE SECTION.
01  WS-MASTER-STATUS      PIC X(2).
01  WS-STATUS-DETAILS.
    05  WS-STATUS-1       PIC X.
    05  WS-STATUS-2       PIC X.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    OPEN I-O MASTER-FILE
    PERFORM VALIDATE-STATUS "OPEN"
    
    * Try various operations and validate status
    PERFORM TEST-READ-OPERATION
    PERFORM TEST-WRITE-OPERATION
    PERFORM TEST-DELETE-OPERATION
    PERFORM TEST-START-OPERATION
    
    CLOSE MASTER-FILE
    PERFORM VALIDATE-STATUS "CLOSE"
    
    STOP RUN.
 
VALIDATE-STATUS.
    USING OPERATION-TYPE.
    
    * Split status code for detailed analysis
    MOVE WS-MASTER-STATUS TO WS-STATUS-DETAILS
    
    * Check first digit (major category)
    EVALUATE WS-STATUS-1
        WHEN "0"
            DISPLAY OPERATION-TYPE " successful"
        WHEN "1"
            DISPLAY OPERATION-TYPE " - End of file or invalid key"
        WHEN "2"
            DISPLAY OPERATION-TYPE " - Record not found or duplicate"
        WHEN "3"
            DISPLAY OPERATION-TYPE " - Permanent error"
        WHEN "4"
            DISPLAY OPERATION-TYPE " - Logic error"
        WHEN "9"
            DISPLAY OPERATION-TYPE " - Implementation-specific error"
        WHEN OTHER
            DISPLAY OPERATION-TYPE " - Unknown status category"
    END-EVALUATE
    
    * Check second digit (specific error)
    EVALUATE WS-STATUS-2
        WHEN "0"
            DISPLAY "  Specific: No additional information"
        WHEN "1"
            DISPLAY "  Specific: File not found"
        WHEN "2"
            DISPLAY "  Specific: File already exists"
        WHEN "3"
            DISPLAY "  Specific: File access denied"
        WHEN "4"
            DISPLAY "  Specific: File already open"
        WHEN "5"
            DISPLAY "  Specific: File not open"
        WHEN "6"
            DISPLAY "  Specific: File position error"
        WHEN "7"
            DISPLAY "  Specific: File structure error"
        WHEN "8"
            DISPLAY "  Specific: File system error"
        WHEN "9"
            DISPLAY "  Specific: Implementation-specific"
        WHEN OTHER
            DISPLAY "  Specific: Unknown error code"
    END-EVALUATE.
 
TEST-READ-OPERATION.
    MOVE 12345 TO MST-KEY
    READ MASTER-FILE
    PERFORM VALIDATE-STATUS "READ".
 
TEST-WRITE-OPERATION.
    MOVE 99999 TO MST-KEY
    MOVE "TEST-KEY" TO MST-ALT-KEY
    MOVE "Test data for new record" TO MST-DATA
    WRITE MASTER-RECORD
    PERFORM VALIDATE-STATUS "WRITE".
 
TEST-DELETE-OPERATION.
    MOVE 99999 TO MST-KEY
    DELETE MASTER-FILE
    PERFORM VALIDATE-STATUS "DELETE".
 
TEST-START-OPERATION.
    MOVE 12345 TO MST-KEY
    START MASTER-FILE KEY IS GREATER THAN MST-KEY
    PERFORM VALIDATE-STATUS "START".

Explanation: This example shows detailed status code validation by breaking down the two-character status code into its components. The first digit indicates the major category (success, end of file, record not found, permanent error, etc.), while the second digit provides more specific information about the error. This approach allows for very detailed error analysis and helps in debugging complex file operation issues. The program tests various file operations and provides detailed feedback about each operation's result.

Best Practices and Considerations

Important Considerations

  • Always check status codes after file operations
  • Use descriptive names for status fields
  • Handle all possible status codes, not just success
  • Consider creating status validation subroutines
  • Document status code meanings for your application

Advantages

  • Provides standardized error handling
  • Enables detailed error analysis
  • Improves program reliability
  • Facilitates debugging and maintenance
  • Supports multiple file operations

Limitations

  • Status codes may vary between implementations
  • Requires additional code for error handling
  • May not provide detailed error information
  • Status field must be defined for each file
  • Can add complexity to simple programs

Best Practices

  • • Always check status codes after file operations
  • • Use consistent naming conventions for status fields
  • • Create reusable status validation subroutines
  • • Handle all possible error conditions
  • • Document status code meanings and handling

Test Your Knowledge

1. What is the primary purpose of the STATUS clause in COBOL?

  • To define file names
  • To specify file status fields for error handling
  • To set file permissions
  • To define file organization

2. In which COBOL division is the STATUS clause typically used?

  • IDENTIFICATION DIVISION
  • ENVIRONMENT DIVISION
  • DATA DIVISION
  • PROCEDURE DIVISION

3. What data type is typically used for STATUS fields?

  • PIC 9(2)
  • PIC X(2)
  • PIC 9(4)
  • PIC X(4)

4. What does a status code of "00" typically indicate?

  • File not found
  • Successful operation
  • File access denied
  • End of file

5. Can the STATUS clause be used with all file organization types?

  • No, only with sequential files
  • Yes, with all file organization types
  • Only with indexed files
  • Only with relative files

Related Concepts

FILE SECTION

Section for defining file structures and characteristics

File Processing

Techniques for reading, writing, and manipulating files

Error Handling

Methods for handling program errors and exceptions

File Organization

Different ways to organize file data

File Status Error Handling

Specific techniques for handling file status errors

STATICSTOP