MainframeMaster

COBOL Tutorial

Data Validation Techniques in COBOL

Progress0 of 0 lessons

Input Data Validation Methods

Data validation is a critical component of any COBOL application. It ensures that input data meets the required format, type, and business rules before processing. Proper validation helps prevent errors, system crashes, and data integrity issues.

Validation Strategy

  • Validate data as early as possible in the processing flow
  • Implement multiple layers of validation (field level, record level, cross-record)
  • Provide clear error messages that identify the specific validation failure
  • Log validation errors for analysis and reporting
  • Establish consistent error handling procedures

Common Validation Techniques

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
* Using condition names (88-level items)
01  TRANSACTION-TYPE      PIC X.
    88  VALID-TRANS-TYPE  VALUE "A" "D" "U" "I".
 
IF NOT VALID-TRANS-TYPE
   PERFORM INVALID-TRANS-TYPE-ERROR
   EXIT PARAGRAPH
END-IF.
 
* Using class conditions
IF NOT INPUT-AMOUNT IS NUMERIC
   PERFORM INVALID-AMOUNT-ERROR
   EXIT PARAGRAPH
END-IF.
 
* Using relational conditions
IF INPUT-QUANTITY <= ZERO OR INPUT-QUANTITY > 9999
   PERFORM INVALID-QUANTITY-ERROR
   EXIT PARAGRAPH
END-IF.

These basic techniques can be combined to create comprehensive validation logic.

Comprehensive Field Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
VALIDATE-CUSTOMER-RECORD.
    PERFORM VALIDATE-CUSTOMER-ID.
    IF VALID-DATA
       PERFORM VALIDATE-CUSTOMER-NAME
    END-IF.
    IF VALID-DATA
       PERFORM VALIDATE-CUSTOMER-ADDRESS
    END-IF.
    IF VALID-DATA
       PERFORM VALIDATE-CUSTOMER-PHONE
    END-IF.
    EXIT.
 
VALIDATE-CUSTOMER-ID.
    IF CUSTOMER-ID IS NOT NUMERIC
       MOVE "Customer ID must be numeric" TO ERROR-MESSAGE
       MOVE "CUSTOMER-ID" TO ERROR-FIELD
       MOVE "E001" TO ERROR-CODE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF.
    IF CUSTOMER-ID < 100000 OR CUSTOMER-ID > 999999
       MOVE "Customer ID must be 6 digits" TO ERROR-MESSAGE
       MOVE "CUSTOMER-ID" TO ERROR-FIELD
       MOVE "E002" TO ERROR-CODE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF.
    MOVE "Y" TO VALID-DATA.
    EXIT.

A modular approach with dedicated validation routines for each field helps maintain organization and readability.

Required Fields Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
VALIDATE-REQUIRED-FIELDS.
    IF CUSTOMER-NAME = SPACES
       MOVE "Customer name is required" TO ERROR-MESSAGE
       MOVE "CUSTOMER-NAME" TO ERROR-FIELD
       MOVE "E010" TO ERROR-CODE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF.
    IF CUSTOMER-ADDRESS = SPACES
       MOVE "Customer address is required" TO ERROR-MESSAGE
       MOVE "CUSTOMER-ADDRESS" TO ERROR-FIELD
       MOVE "E011" TO ERROR-CODE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF.
    MOVE "Y" TO VALID-DATA.
    EXIT.

Checking for required fields ensures that all necessary data is provided before processing.

Numeric Data Validation

Numeric data validation is essential for financial and calculation-intensive COBOL applications. It ensures that numeric fields contain valid digits, are within acceptable ranges, and follow required formats.

Class Condition Checks

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
* Basic numeric check
IF INPUT-AMOUNT IS NOT NUMERIC
   MOVE "Amount must contain only numeric digits" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Checking for sign
IF INPUT-BALANCE IS NOT NUMERIC
   MOVE "Balance must be numeric" TO ERROR-MESSAGE
ELSE
   IF INPUT-BALANCE IS NEGATIVE AND ACCOUNT-TYPE = "S"
      MOVE "Savings account cannot have negative balance" TO ERROR-MESSAGE
      MOVE "N" TO VALID-DATA
   END-IF
END-IF.
 
* Other class conditions
IF INPUT-NAME IS NOT ALPHABETIC
   MOVE "Name must contain only letters" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
IF INPUT-CODE IS NOT ALPHANUMERIC
   MOVE "Code must be alphanumeric" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.

COBOL provides built-in class conditions to check the type of data in a field.

Range Validation for Numeric Fields

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
* Simple range check
IF INTEREST-RATE < 0.01 OR INTEREST-RATE > 30.00
   MOVE "Interest rate must be between 0.01 and 30.00" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Using 88-level conditions for ranges
01  STUDENT-GRADE         PIC 999V9.
    88  VALID-GRADE       VALUE 0 THRU 100.
    88  PASSING-GRADE     VALUE 60 THRU 100.
    88  FAILING-GRADE     VALUE 0 THRU 59.9.
    
IF NOT VALID-GRADE
   MOVE "Grade must be between 0 and 100" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Complex checks based on other fields
EVALUATE TRUE
    WHEN ACCOUNT-TYPE = "S" AND WITHDRAWAL-AMOUNT > CURRENT-BALANCE
         MOVE "Insufficient funds in savings account" TO ERROR-MESSAGE
         MOVE "N" TO VALID-DATA
    WHEN ACCOUNT-TYPE = "C" AND WITHDRAWAL-AMOUNT > 
                             (CURRENT-BALANCE + OVERDRAFT-LIMIT)
         MOVE "Amount exceeds available funds and overdraft" TO ERROR-MESSAGE
         MOVE "N" TO VALID-DATA
END-EVALUATE.

Range checks ensure that numeric values fall within acceptable business limits.

Decimal and Scale Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
* Check for proper decimal alignment
01  NUMERIC-WORK-AREAS.
    05  DECIMAL-CHECK     PIC 9(5)V99.
    05  DECIMAL-STRING REDEFINES DECIMAL-CHECK PIC X(7).
    05  DECIMAL-PARTS.
        10  WHOLE-PART    PIC X(5).
        10  DECIMAL-POINT PIC X VALUE ".".
        10  FRAC-PART     PIC X(2).
 
VALIDATE-DECIMAL-FORMAT.
    MOVE INPUT-AMOUNT TO DECIMAL-CHECK
    MOVE DECIMAL-CHECK TO DECIMAL-PARTS
    
    IF DECIMAL-STRING IS NOT NUMERIC
       MOVE "Amount must be numeric" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
    ELSE
       IF FRAC-PART = "00" OR FRAC-PART = "50"
          CONTINUE
       ELSE
          MOVE "Cents must be either .00 or .50" TO ERROR-MESSAGE
          MOVE "N" TO VALID-DATA
       END-IF
    END-IF.

Some business rules require validating the decimal portion of numeric values.

Mathematical Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
* Check digit validation (simplified example)
VALIDATE-ACCOUNT-NUMBER.
    MOVE ZERO TO CHECKSUM
    MOVE ZERO TO POSITION
    
    PERFORM VARYING POSITION FROM 1 BY 1
            UNTIL POSITION > 9
        COMPUTE DIGIT = FUNCTION NUMVAL(ACCOUNT-NUMBER(POSITION:1))
        COMPUTE WEIGHT = 10 - POSITION
        COMPUTE CHECKSUM = CHECKSUM + (DIGIT * WEIGHT)
    END-PERFORM
    
    COMPUTE EXPECTED-CHECK-DIGIT = FUNCTION MOD(CHECKSUM 11)
    COMPUTE ACTUAL-CHECK-DIGIT = 
            FUNCTION NUMVAL(ACCOUNT-NUMBER(10:1))
            
    IF EXPECTED-CHECK-DIGIT NOT = ACTUAL-CHECK-DIGIT
       MOVE "Invalid account number (check digit failed)" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
    END-IF.
 
* Total verification
IF ORDER-TOTAL NOT = SUBTOTAL + TAX-AMOUNT - DISCOUNT-AMOUNT
   MOVE "Order total does not match calculated amount" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.

Mathematical validation can include check digits, cross-field calculations, and total verification.

Date and Code Validation

Date validation is one of the most common and important validation tasks in COBOL applications. Improper date validation can lead to processing errors, incorrect calculations, and even system failures.

Basic Date Format Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
* Validate date in YYYYMMDD format
01  WS-DATE              PIC X(8).
01  WS-DATE-PARTS REDEFINES WS-DATE.
    05  WS-YEAR          PIC X(4).
    05  WS-MONTH         PIC X(2).
    05  WS-DAY           PIC X(2).
    
VALIDATE-DATE-FORMAT.
    MOVE INPUT-DATE TO WS-DATE
    
    * Check if all parts are numeric
    IF WS-DATE IS NOT NUMERIC
       MOVE "Date must contain only digits" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * Check month range
    IF WS-MONTH < "01" OR WS-MONTH > "12"
       MOVE "Month must be between 01 and 12" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * Check day range (simplified)
    IF WS-DAY < "01" OR WS-DAY > "31"
       MOVE "Day must be between 01 and 31" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * More detailed validation for days per month would go here
    
    MOVE "Y" TO VALID-DATA.
    EXIT.

Basic date validation checks that the format is correct and the components are within valid ranges.

Comprehensive Date Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
01  DATE-VALIDATION-AREAS.
    05  WS-DATE              PIC X(8).
    05  WS-DATE-NUM          PIC 9(8).
    05  WS-DATE-PARTS REDEFINES WS-DATE-NUM.
        10  WS-YEAR          PIC 9(4).
        10  WS-MONTH         PIC 9(2).
        10  WS-DAY           PIC 9(2).
    05  WS-DAYS-IN-MONTH     PIC 9(2) VALUE ZEROS.
    05  WS-DATE-INTEGER      PIC 9(8) VALUE ZEROS.
    
VALIDATE-DATE.
    MOVE INPUT-DATE TO WS-DATE
    
    * Check if all parts are numeric
    IF WS-DATE IS NOT NUMERIC
       MOVE "Date must contain only digits" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    MOVE WS-DATE TO WS-DATE-NUM
    
    * Check year range for business requirements
    IF WS-YEAR < 1900 OR WS-YEAR > 2100
       MOVE "Year must be between 1900 and 2100" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * Check month range
    IF WS-MONTH < 1 OR WS-MONTH > 12
       MOVE "Month must be between 01 and 12" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * Determine days in month (simplified)
    EVALUATE WS-MONTH
        WHEN 1 WHEN 3 WHEN 5 WHEN 7 WHEN 8 WHEN 10 WHEN 12
             MOVE 31 TO WS-DAYS-IN-MONTH
        WHEN 4 WHEN 6 WHEN 9 WHEN 11
             MOVE 30 TO WS-DAYS-IN-MONTH
        WHEN 2
             COMPUTE WS-DAYS-IN-MONTH = 28 +
                ((WS-YEAR FUNCTION MOD 4 = 0) AND NOT
                 (WS-YEAR FUNCTION MOD 100 = 0) OR
                 (WS-YEAR FUNCTION MOD 400 = 0))
    END-EVALUATE
    
    * Check day range
    IF WS-DAY < 1 OR WS-DAY > WS-DAYS-IN-MONTH
       MOVE "Day is not valid for the specified month and year" 
            TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    * For more advanced validation, convert to integer date
    * and check if conversion works
    COMPUTE WS-DATE-INTEGER = FUNCTION INTEGER-OF-DATE(WS-DATE-NUM)
    
    IF WS-DATE-INTEGER = 0
       MOVE "Invalid date format" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    MOVE "Y" TO VALID-DATA.
    EXIT.

Comprehensive date validation includes checking for leap years and using built-in functions to verify date validity.

Code and ID Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
* Validate product code format (example: ABC-12345)
VALIDATE-PRODUCT-CODE.
    IF PRODUCT-CODE(1:3) IS NOT ALPHABETIC
       MOVE "Product code must start with 3 letters" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    IF PRODUCT-CODE(4:1) NOT = "-"
       MOVE "Product code must have hyphen at position 4" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    IF PRODUCT-CODE(5:5) IS NOT NUMERIC
       MOVE "Product code must end with 5 digits" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    PERFORM CHECK-PRODUCT-EXISTS
    
    IF PRODUCT-EXISTS = "N"
       MOVE "Product code not found in product master" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    MOVE "Y" TO VALID-DATA.
    EXIT.
 
* Validate social security number (XXX-XX-XXXX)
VALIDATE-SSN.
    IF SSN-INPUT(4:1) NOT = "-" OR SSN-INPUT(7:1) NOT = "-"
       MOVE "SSN must be in format XXX-XX-XXXX" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    IF SSN-PART1 IS NOT NUMERIC OR
       SSN-PART2 IS NOT NUMERIC OR
       SSN-PART3 IS NOT NUMERIC
       MOVE "SSN must contain only digits and hyphens" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    IF SSN-PART1 = "000" OR
       SSN-PART2 = "00" OR
       SSN-PART3 = "0000"
       MOVE "SSN cannot have all zeros in any part" TO ERROR-MESSAGE
       MOVE "N" TO VALID-DATA
       EXIT PARAGRAPH
    END-IF
    
    MOVE "Y" TO VALID-DATA.
    EXIT.

Code validation often involves checking specific formats and patterns required by business rules.

Range Checking Techniques

Range checking ensures that data values fall within acceptable limits defined by business rules. It is a fundamental aspect of data validation in COBOL applications.

Simple Range Checks

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
* Basic numeric range check
IF QUANTITY < 1 OR QUANTITY > 999
   MOVE "Quantity must be between 1 and 999" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Date range check
IF ORDER-DATE < CURRENT-DATE - 30
   MOVE "Order date cannot be more than 30 days in the past" 
        TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
IF DELIVERY-DATE < CURRENT-DATE
   MOVE "Delivery date cannot be in the past" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.

Simple range checks compare values against minimum and maximum bounds.

Using 88-Level Items for Ranges

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
01  STUDENT-AGE           PIC 999.
    88  VALID-STUDENT-AGE  VALUE 18 THRU 65.
    88  MINOR-STUDENT      VALUE 18 THRU 20.
    88  ADULT-STUDENT      VALUE 21 THRU 65.
 
01  PRODUCT-QUANTITY      PIC 9(5).
    88  VALID-QUANTITY     VALUE 1 THRU 10000.
    88  SMALL-ORDER        VALUE 1 THRU 10.
    88  MEDIUM-ORDER       VALUE 11 THRU 100.
    88  LARGE-ORDER        VALUE 101 THRU 1000.
    88  BULK-ORDER         VALUE 1001 THRU 10000.
 
* Using the 88-level items in validation
IF NOT VALID-STUDENT-AGE
   MOVE "Student age must be between 18 and 65" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
IF NOT VALID-QUANTITY
   MOVE "Quantity must be between 1 and 10000" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Additional processing based on range categories
IF SMALL-ORDER
   MOVE 0 TO DISCOUNT-PERCENT
ELSE IF MEDIUM-ORDER
   MOVE 5 TO DISCOUNT-PERCENT
ELSE IF LARGE-ORDER
   MOVE 10 TO DISCOUNT-PERCENT
ELSE IF BULK-ORDER
   MOVE 15 TO DISCOUNT-PERCENT
END-IF.

88-level items provide a readable way to define and check ranges with descriptive names.

Dynamic Range Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
* Validating against dynamically determined limits
01  CREDIT-LIMIT-TABLE.
    05  CREDIT-LIMITS OCCURS 5 TIMES INDEXED BY CL-IDX.
        10  CUSTOMER-TYPE     PIC X.
        10  MIN-CREDIT-SCORE  PIC 9(3).
        10  MAX-CREDIT-AMT    PIC 9(7)V99.
 
* Initialize the table (would typically be loaded from a file)
INITIALIZE-CREDIT-LIMITS.
    MOVE "R" TO CUSTOMER-TYPE (1)
    MOVE 500 TO MIN-CREDIT-SCORE (1)
    MOVE 5000.00 TO MAX-CREDIT-AMT (1)
    
    MOVE "P" TO CUSTOMER-TYPE (2)
    MOVE 600 TO MIN-CREDIT-SCORE (2)
    MOVE 10000.00 TO MAX-CREDIT-AMT (2)
    
    MOVE "G" TO CUSTOMER-TYPE (3)
    MOVE 550 TO MIN-CREDIT-SCORE (3)
    MOVE 15000.00 TO MAX-CREDIT-AMT (3)
    
    MOVE "C" TO CUSTOMER-TYPE (4)
    MOVE 700 TO MIN-CREDIT-SCORE (4)
    MOVE 25000.00 TO MAX-CREDIT-AMT (4)
    
    MOVE "V" TO CUSTOMER-TYPE (5)
    MOVE 750 TO MIN-CREDIT-SCORE (5)
    MOVE 50000.00 TO MAX-CREDIT-AMT (5)
    EXIT.
 
* Validate loan amount against dynamic limits
VALIDATE-LOAN-AMOUNT.
    SET CL-IDX TO 1
    SEARCH CREDIT-LIMITS
       AT END
          MOVE "Invalid customer type" TO ERROR-MESSAGE
          MOVE "N" TO VALID-DATA
       WHEN CUSTOMER-TYPE (CL-IDX) = INPUT-CUSTOMER-TYPE
          IF INPUT-CREDIT-SCORE < MIN-CREDIT-SCORE (CL-IDX)
             MOVE "Credit score too low for this customer type"
                  TO ERROR-MESSAGE
             MOVE "N" TO VALID-DATA
          ELSE
             IF INPUT-LOAN-AMOUNT > MAX-CREDIT-AMT (CL-IDX)
                MOVE "Loan amount exceeds maximum for this customer"
                     TO ERROR-MESSAGE
                MOVE "N" TO VALID-DATA
             ELSE
                MOVE "Y" TO VALID-DATA
             END-IF
          END-IF
    END-SEARCH
    EXIT.

Dynamic range validation uses tables or conditional logic to determine appropriate limits based on other data values.

Cross-Field Range Validation

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
* Ensuring that one value is less than or equal to another
IF ORDER-QUANTITY > INVENTORY-QUANTITY
   MOVE "Order quantity exceeds available inventory" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Validating date ranges
IF END-DATE < START-DATE
   MOVE "End date cannot be earlier than start date" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
IF END-DATE > START-DATE + 365
   MOVE "Date range cannot exceed one year" TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
* Validating financial boundaries
IF PAYMENT-AMOUNT > INVOICE-AMOUNT * 1.10
   MOVE "Payment cannot exceed invoice amount by more than 10%" 
        TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.
 
IF DISCOUNT-AMOUNT > INVOICE-AMOUNT * 0.25
   MOVE "Discount cannot exceed 25% of invoice amount" 
        TO ERROR-MESSAGE
   MOVE "N" TO VALID-DATA
END-IF.

Cross-field validation ensures that relationships between multiple fields are logically consistent.

Error Handling for Invalid Data

Proper error handling is a critical component of data validation. It ensures that validation failures are reported clearly, consistently, and in a way that facilitates resolution.

Centralized Error Handling

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
01  ERROR-HANDLING-FIELDS.
    05  ERROR-SWITCH       PIC X VALUE "N".
        88  ERROR-FOUND    VALUE "Y".
        88  NO-ERROR       VALUE "N".
    05  ERROR-MESSAGE      PIC X(80) VALUE SPACES.
    05  ERROR-CODE         PIC X(4) VALUE SPACES.
    05  ERROR-FIELD        PIC X(30) VALUE SPACES.
    05  ERROR-TABLE.
        10  ERROR-ENTRY OCCURS 50 TIMES INDEXED BY ERR-IDX.
            15  ERR-CODE   PIC X(4).
            15  ERR-FIELD  PIC X(30).
            15  ERR-MESSAGE PIC X(80).
    05  ERROR-COUNT        PIC 9(2) VALUE ZERO.
 
HANDLE-VALIDATION-ERROR.
    SET ERROR-FOUND TO TRUE
    ADD 1 TO ERROR-COUNT
    
    MOVE ERROR-CODE TO ERR-CODE (ERROR-COUNT)
    MOVE ERROR-FIELD TO ERR-FIELD (ERROR-COUNT)
    MOVE ERROR-MESSAGE TO ERR-MESSAGE (ERROR-COUNT)
    
    * Write to error log
    WRITE ERROR-LOG-RECORD FROM ERROR-HANDLING-FIELDS
    
    * For interactive programs, display error
    DISPLAY ERROR-MESSAGE
    
    EXIT.
 
LOG-ALL-ERRORS.
    IF NO-ERROR
       EXIT PARAGRAPH
    END-IF
    
    PERFORM VARYING ERR-IDX FROM 1 BY 1
            UNTIL ERR-IDX > ERROR-COUNT
        WRITE ERROR-REPORT-LINE FROM ERR-ENTRY (ERR-IDX)
    END-PERFORM
    
    EXIT.

A centralized error handling approach provides consistency and makes errors easier to track and resolve.

Error Processing Strategy

  • Detect errors as early as possible in the processing flow
  • Provide specific, actionable error messages
  • Include error codes for easy reference and categorization
  • Identify the specific field or record that failed validation
  • Collect multiple errors before stopping processing when possible
  • Log errors for analysis and reporting
  • Follow consistent error handling procedures across the application

Batch Processing Error Handling

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
01  PROCESSING-SWITCHES.
    05  END-OF-FILE-SW     PIC X VALUE "N".
        88  END-OF-FILE    VALUE "Y".
    05  VALID-RECORD-SW    PIC X VALUE "Y".
        88  VALID-RECORD   VALUE "Y".
        88  INVALID-RECORD VALUE "N".
 
PROCESS-INPUT-FILE.
    OPEN INPUT INPUT-FILE
         OUTPUT VALID-OUTPUT-FILE
         OUTPUT ERROR-FILE
    
    READ INPUT-FILE
         AT END SET END-OF-FILE TO TRUE
    END-READ
    
    PERFORM UNTIL END-OF-FILE
        MOVE "Y" TO VALID-RECORD-SW
        INITIALIZE ERROR-COUNT
        
        PERFORM VALIDATE-INPUT-RECORD
        
        IF VALID-RECORD
           WRITE VALID-OUTPUT-RECORD FROM INPUT-RECORD
        ELSE
           MOVE INPUT-RECORD TO ERROR-RECORD
           MOVE ERROR-COUNT TO ERROR-RECORD-COUNT
           WRITE ERROR-OUTPUT-RECORD FROM ERROR-RECORD
        END-IF
        
        READ INPUT-FILE
             AT END SET END-OF-FILE TO TRUE
        END-READ
    END-PERFORM
    
    CLOSE INPUT-FILE
          VALID-OUTPUT-FILE
          ERROR-FILE
    EXIT.
 
VALIDATE-INPUT-RECORD.
    PERFORM VALIDATE-CUSTOMER-ID
    PERFORM VALIDATE-TRANSACTION-DATE
    PERFORM VALIDATE-TRANSACTION-AMOUNT
    PERFORM VALIDATE-TRANSACTION-TYPE
    EXIT.
 
VALIDATE-CUSTOMER-ID.
    IF CUSTOMER-ID IS NOT NUMERIC
       MOVE "E001" TO ERROR-CODE
       MOVE "CUSTOMER-ID" TO ERROR-FIELD
       MOVE "Customer ID must be numeric" TO ERROR-MESSAGE
       PERFORM HANDLE-VALIDATION-ERROR
       SET INVALID-RECORD TO TRUE
    END-IF
    EXIT.

Batch programs often collect all validation errors before rejecting a record, writing invalid records to an error file for later correction.

Error Severity Levels

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
01  ERROR-LEVELS.
    05  INFO-LEVEL         PIC X VALUE "I".
    05  WARNING-LEVEL      PIC X VALUE "W".
    05  ERROR-LEVEL        PIC X VALUE "E".
    05  CRITICAL-LEVEL     PIC X VALUE "C".
    
01  ERROR-RECORD.
    05  ERR-SEVERITY       PIC X.
    05  ERR-CODE           PIC X(4).
    05  ERR-FIELD          PIC X(30).
    05  ERR-MESSAGE        PIC X(80).
    05  ERR-TIMESTAMP      PIC X(26).
 
RECORD-ERROR.
    MOVE FUNCTION CURRENT-DATE TO ERR-TIMESTAMP
    WRITE ERROR-LOG-RECORD FROM ERROR-RECORD
    
    * For critical errors, terminate processing
    IF ERR-SEVERITY = CRITICAL-LEVEL
       DISPLAY "CRITICAL ERROR: " ERR-CODE " - " ERR-MESSAGE
       MOVE 16 TO RETURN-CODE
       STOP RUN
    END-IF
    
    * For regular errors, mark record as invalid
    IF ERR-SEVERITY = ERROR-LEVEL
       SET INVALID-RECORD TO TRUE
    END-IF
    
    EXIT.

Using error severity levels helps determine the appropriate response to different types of validation failures.

Reporting Validation Errors

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
01  ERROR-STATISTICS.
    05  TOTAL-RECORDS-READ    PIC 9(7) VALUE ZERO.
    05  VALID-RECORD-COUNT    PIC 9(7) VALUE ZERO.
    05  ERROR-RECORD-COUNT    PIC 9(7) VALUE ZERO.
    05  ERROR-COUNTS.
        10  FORMAT-ERRORS     PIC 9(5) VALUE ZERO.
        10  RANGE-ERRORS      PIC 9(5) VALUE ZERO.
        10  LOGIC-ERRORS      PIC 9(5) VALUE ZERO.
        10  MISSING-ERRORS    PIC 9(5) VALUE ZERO.
 
PRINT-VALIDATION-REPORT.
    MOVE SPACES TO REPORT-LINE
    
    MOVE "VALIDATION REPORT" TO RL-TITLE
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE SPACES TO REPORT-LINE
    MOVE "Total Records Processed:" TO RL-LABEL
    MOVE TOTAL-RECORDS-READ TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Valid Records:" TO RL-LABEL
    MOVE VALID-RECORD-COUNT TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Records with Errors:" TO RL-LABEL
    MOVE ERROR-RECORD-COUNT TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE SPACES TO REPORT-LINE
    MOVE "ERROR BREAKDOWN" TO RL-TITLE
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Format Errors:" TO RL-LABEL
    MOVE FORMAT-ERRORS TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Range Errors:" TO RL-LABEL
    MOVE RANGE-ERRORS TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Logic Errors:" TO RL-LABEL
    MOVE LOGIC-ERRORS TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    MOVE "Missing Required Data:" TO RL-LABEL
    MOVE MISSING-ERRORS TO RL-COUNT
    WRITE REPORT-RECORD FROM REPORT-LINE
    
    EXIT.

Providing detailed error reports helps users and administrators understand and address validation issues.

Exercise: Implementing Data Validation

Complete the following COBOL program by implementing validation routines for each field in the customer record:

cobol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
IDENTIFICATION DIVISION.
PROGRAM-ID. DATAVAL.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID         PIC X(6).
    05  CUSTOMER-NAME       PIC X(30).
    05  CUSTOMER-ADDRESS    PIC X(50).
    05  CUSTOMER-CITY       PIC X(20).
    05  CUSTOMER-STATE      PIC XX.
    05  CUSTOMER-ZIP        PIC X(10).
    05  CUSTOMER-PHONE      PIC X(14).
    05  CUSTOMER-DOB        PIC X(10).
    05  CUSTOMER-CREDIT-LIM PIC 9(7)V99.
    05  CUSTOMER-TYPE       PIC X.
        88  RETAIL          VALUE "R".
        88  WHOLESALE       VALUE "W".
        88  DISTRIBUTOR     VALUE "D".
        88  VALID-CUST-TYPE VALUE "R" "W" "D".
 
01  VALIDATION-FIELDS.
    05  VALID-DATA-SW       PIC X VALUE "Y".
        88  VALID-DATA      VALUE "Y".
        88  INVALID-DATA    VALUE "N".
    05  ERROR-MESSAGE       PIC X(80) VALUE SPACES.
 
* Add working storage areas for date validation, state code validation,
* phone number format checking, etc.
 
PROCEDURE DIVISION.
    DISPLAY "Data Validation Exercise".
    
    * Initialize sample data
    MOVE "ID1234" TO CUSTOMER-ID
    MOVE "John Doe" TO CUSTOMER-NAME
    MOVE "123 Main St" TO CUSTOMER-ADDRESS
    MOVE "Springfield" TO CUSTOMER-CITY
    MOVE "XX" TO CUSTOMER-STATE
    MOVE "12345-6789" TO CUSTOMER-ZIP
    MOVE "(555) 123-4567" TO CUSTOMER-PHONE
    MOVE "13/25/2000" TO CUSTOMER-DOB
    MOVE 25000.00 TO CUSTOMER-CREDIT-LIM
    MOVE "Q" TO CUSTOMER-TYPE
    
    * Perform validation
    PERFORM VALIDATE-CUSTOMER-RECORD
    
    IF VALID-DATA
       DISPLAY "Customer record is valid"
    ELSE
       DISPLAY "Customer record is invalid"
    END-IF
    
    STOP RUN.
 
VALIDATE-CUSTOMER-RECORD.
    MOVE "Y" TO VALID-DATA-SW
    
    * Implement validation for each field:
    
    * 1. CUSTOMER-ID should be 6 characters, start with 2 letters followed by 4 digits
    
    * 2. CUSTOMER-NAME should not be spaces and be at least 3 characters
    
    * 3. CUSTOMER-STATE should be a valid US state code
    
    * 4. CUSTOMER-ZIP should be in format 12345 or 12345-6789
    
    * 5. CUSTOMER-PHONE should be in format (XXX) XXX-XXXX
    
    * 6. CUSTOMER-DOB should be in format MM/DD/YYYY and be a valid date
    *    (customer must be at least 18 years old and not born before 1900)
    
    * 7. CUSTOMER-CREDIT-LIM should be between 0 and 100000.00
    
    * 8. CUSTOMER-TYPE should be a valid type (R, W, or D)
    
    EXIT.

Complete the validation routines for each field in the CUSTOMER-RECORD, implementing appropriate error handling for each validation failure.

Knowledge Check

Test Your Knowledge

1. Which COBOL statement is commonly used to check if a field contains numeric data?

  • IF NUMERIC-FIELD IS NUMERIC
  • IF NUMERIC-FIELD CONTAINS NUMBERS
  • IF NUMERIC-FIELD IS NUMBER
  • IF NUMERIC-FIELD MATCHES "9(5)"

2. What is the best way to validate a date field in COBOL?

  • Using the DATE-VALIDATION function
  • Converting to internal date format and checking for errors
  • Using 88-level items for every valid date
  • Comparing with CURRENT-DATE

3. Which of the following is NOT a common technique for handling invalid data in COBOL?

  • Displaying an error message
  • Writing to an error log file
  • Setting a return code
  • Automatically correcting the data without notification

4. What is the purpose of range checking in data validation?

  • To ensure data is sorted in ascending order
  • To verify that a value falls within acceptable minimum and maximum values
  • To check if data contains only characters from a specific range of the ASCII table
  • To validate that array indices are within bounds

5. Which of the following is an example of defensive programming in COBOL data validation?

  • Assuming all input data is correct to improve performance
  • Validating data only after writing it to a database
  • Checking for both the presence of required data and the validity of its format/content
  • Using generic error messages for all validation failures

Frequently Asked Questions

Working with Conditional VariablesInternal Data Manipulation