COBOL Tutorial

COBOL Migration and Modernization

Progress0 of 0 lessons

COBOL (Common Business-Oriented Language) migration and modernization represents one of the most critical challenges facing enterprise IT today. With billions of lines of COBOL code powering core business systems across industries, organizations must balance preserving decades of business logic while adapting to modern technological requirements. This comprehensive guide covers strategies, tools, and techniques for successful COBOL transformation projects.

Key Modernization Drivers

Skills Gap: Aging COBOL workforce and decreasing pool of experienced developers
Hardware Costs: Expensive mainframe MIPS (Million Instructions Per Second) and maintenance
Agility Requirements: Need for faster development cycles and continuous deployment
Integration Demands: Connecting legacy systems with modern APIs and microservices
Cloud Strategy: Moving to scalable, cost-effective cloud infrastructure

Migrating Legacy COBOL Applications

Legacy COBOL migration involves multiple strategies depending on business requirements, technical constraints, and budget considerations. Understanding these approaches is crucial for making informed decisions about your modernization journey.

Migration Strategy Overview

Rehost (Lift & Shift)

Move existing COBOL applications to new platforms with minimal changes.

Fastest approach
Lowest risk
Limited benefits
Maintains technical debt

Replatform

Optimize applications for new platforms while preserving core architecture.

Moderate complexity
Some optimization
Better performance
Reduced costs

Refactor/Rearchitect

Reimagine applications using modern architectures and technologies.

Highest complexity
Maximum benefits
Modern capabilities
Long-term value

Migration Assessment Framework

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
IDENTIFICATION DIVISION.
PROGRAM-ID. MIGRATION-ASSESSOR.
 
* Migration Assessment Tool
* Purpose: Analyze COBOL programs for modernization readiness
* Author: Migration Team
* Date: 2024
 
DATA DIVISION.
WORKING-STORAGE SECTION.
 
01  WS-ASSESSMENT-CRITERIA.
    05  COMPLEXITY-SCORE        PIC 9(3)V99.
    05  BUSINESS-VALUE          PIC 9(3)V99.
    05  TECHNICAL-DEBT          PIC 9(3)V99.
    05  DEPENDENCY-COUNT        PIC 9(5).
    05  LOC-COUNT              PIC 9(8).    *> Lines of Code
    05  CYCLOMATIC-COMPLEXITY  PIC 9(5).
 
01  WS-MIGRATION-RECOMMENDATION.
    05  STRATEGY-TYPE          PIC X(20).
    05  PRIORITY-LEVEL         PIC X(10).
    05  EFFORT-ESTIMATE        PIC 9(5).    *> Person days
    05  RISK-LEVEL            PIC X(10).
    05  RECOMMENDED-APPROACH   PIC X(100).
 
01  WS-PROGRAM-METRICS.
    05  TOTAL-PARAGRAPHS       PIC 9(5).
    05  TOTAL-COPYBOOKS        PIC 9(3).
    05  DATABASE-CALLS         PIC 9(5).
    05  FILE-OPERATIONS        PIC 9(5).
    05  SCREEN-INTERACTIONS    PIC 9(5).
 
PROCEDURE DIVISION.
MAIN-ASSESSMENT.
    PERFORM ANALYZE-CODE-COMPLEXITY.
    PERFORM EVALUATE-BUSINESS-VALUE.
    PERFORM ASSESS-TECHNICAL-DEBT.
    PERFORM GENERATE-RECOMMENDATION.
    
    DISPLAY "=== COBOL MIGRATION ASSESSMENT ===".
    DISPLAY "Program: " PROGRAM-ID.
    DISPLAY "Lines of Code: " LOC-COUNT.
    DISPLAY "Complexity Score: " COMPLEXITY-SCORE.
    DISPLAY "Business Value: " BUSINESS-VALUE.
    DISPLAY "Recommended Strategy: " STRATEGY-TYPE.
    DISPLAY "Priority Level: " PRIORITY-LEVEL.
    DISPLAY "Estimated Effort: " EFFORT-ESTIMATE " days".
    
    STOP RUN.
 
ANALYZE-CODE-COMPLEXITY.
    * Analyze program structure and complexity
    COMPUTE CYCLOMATIC-COMPLEXITY = 
        (TOTAL-PARAGRAPHS * 1.5) + 
        (DATABASE-CALLS * 2) + 
        (FILE-OPERATIONS * 1.2).
    
    EVALUATE CYCLOMATIC-COMPLEXITY
        WHEN 1 THRU 50
            MOVE 25.00 TO COMPLEXITY-SCORE
        WHEN 51 THRU 100
            MOVE 50.00 TO COMPLEXITY-SCORE
        WHEN 101 THRU 200
            MOVE 75.00 TO COMPLEXITY-SCORE
        WHEN OTHER
            MOVE 100.00 TO COMPLEXITY-SCORE
    END-EVALUATE.
 
EVALUATE-BUSINESS-VALUE.
    * Assess business criticality and usage frequency
    IF SCREEN-INTERACTIONS > 100
        ADD 30 TO BUSINESS-VALUE
    END-IF.
    
    IF DATABASE-CALLS > 50
        ADD 25 TO BUSINESS-VALUE
    END-IF.
    
    IF LOC-COUNT > 10000
        ADD 20 TO BUSINESS-VALUE
    END-IF.
 
ASSESS-TECHNICAL-DEBT.
    * Evaluate maintenance burden and obsolete practices
    COMPUTE TECHNICAL-DEBT = 
        (LOC-COUNT / 1000) + 
        (CYCLOMATIC-COMPLEXITY / 10) + 
        (DEPENDENCY-COUNT * 5).
    
    IF TECHNICAL-DEBT > 100
        MOVE 100.00 TO TECHNICAL-DEBT
    END-IF.
 
GENERATE-RECOMMENDATION.
    * Generate migration strategy recommendation
    EVALUATE TRUE
        WHEN COMPLEXITY-SCORE < 40 AND BUSINESS-VALUE > 60
            MOVE "REPLATFORM" TO STRATEGY-TYPE
            MOVE "HIGH" TO PRIORITY-LEVEL
            COMPUTE EFFORT-ESTIMATE = LOC-COUNT / 500
            MOVE "LOW" TO RISK-LEVEL
            
        WHEN COMPLEXITY-SCORE > 70 AND BUSINESS-VALUE > 80
            MOVE "REFACTOR" TO STRATEGY-TYPE
            MOVE "MEDIUM" TO PRIORITY-LEVEL
            COMPUTE EFFORT-ESTIMATE = LOC-COUNT / 200
            MOVE "HIGH" TO RISK-LEVEL
            
        WHEN BUSINESS-VALUE < 30
            MOVE "RETIRE" TO STRATEGY-TYPE
            MOVE "LOW" TO PRIORITY-LEVEL
            MOVE 30 TO EFFORT-ESTIMATE
            MOVE "LOW" TO RISK-LEVEL
            
        WHEN OTHER
            MOVE "REHOST" TO STRATEGY-TYPE
            MOVE "MEDIUM" TO PRIORITY-LEVEL
            COMPUTE EFFORT-ESTIMATE = LOC-COUNT / 1000
            MOVE "MEDIUM" TO RISK-LEVEL
    END-EVALUATE.

Data Migration Strategies

VSAM to Relational Database Migration

VSAM (Virtual Storage Access Method) is IBM's file access method for mainframes. Migration to relational databases requires careful schema mapping and data transformation.

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
IDENTIFICATION DIVISION.
PROGRAM-ID. VSAM-TO-DB-MIGRATOR.
 
* VSAM to Relational Database Migration Utility
* Converts VSAM KSDS files to SQL database tables
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-VSAM ASSIGN TO "CUSTFILE"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS CUST-ID
        FILE STATUS IS WS-VSAM-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-VSAM.
01  CUSTOMER-RECORD.
    05  CUST-ID           PIC 9(10).
    05  CUST-NAME         PIC X(50).
    05  CUST-ADDRESS      PIC X(100).
    05  CUST-PHONE        PIC X(15).
    05  CUST-EMAIL        PIC X(50).
    05  CUST-BALANCE      PIC S9(11)V99 COMP-3.
    05  CUST-LAST-UPDATE  PIC 9(8).     *> YYYYMMDD
    05  CUST-STATUS       PIC X.
    05  FILLER            PIC X(20).     *> Future expansion
 
WORKING-STORAGE SECTION.
01  WS-VSAM-STATUS        PIC XX.
01  WS-RECORD-COUNT       PIC 9(8) VALUE 0.
01  WS-ERROR-COUNT        PIC 9(5) VALUE 0.
01  WS-SQL-STATEMENT      PIC X(2000).
 
* Database connection variables
01  WS-SQLCODE            PIC S9(9) COMP.
01  WS-SQLSTATE           PIC X(5).
 
* Data conversion work areas
01  WS-CONVERTED-BALANCE  PIC S9(11)V99.
01  WS-FORMATTED-DATE     PIC X(10).   *> YYYY-MM-DD
01  WS-CLEAN-NAME         PIC X(50).
01  WS-CLEAN-ADDRESS      PIC X(100).
 
PROCEDURE DIVISION.
MAIN-MIGRATION.
    PERFORM INITIALIZE-DATABASE.
    PERFORM OPEN-VSAM-FILE.
    PERFORM MIGRATE-RECORDS.
    PERFORM CLOSE-FILES.
    PERFORM GENERATE-MIGRATION-REPORT.
    STOP RUN.
 
INITIALIZE-DATABASE.
    * Connect to target database
    EXEC SQL
        CONNECT TO 'MODERNDB' USER 'MIGUSER' USING 'PASSWORD'
    END-EXEC.
    
    IF SQLCODE NOT = 0
        DISPLAY "Database connection failed: " SQLCODE
        STOP RUN
    END-IF.
    
    * Create target table if it doesn't exist
    EXEC SQL
        CREATE TABLE IF NOT EXISTS CUSTOMERS (
            customer_id     BIGINT PRIMARY KEY,
            customer_name   VARCHAR(50) NOT NULL,
            address         VARCHAR(100),
            phone           VARCHAR(15),
            email           VARCHAR(50),
            balance         DECIMAL(13,2),
            last_update     DATE,
            status          CHAR(1),
            created_date    TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            migrated_date   TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        )
    END-EXEC.
 
OPEN-VSAM-FILE.
    OPEN INPUT CUSTOMER-VSAM.
    IF WS-VSAM-STATUS NOT = "00"
        DISPLAY "Failed to open VSAM file: " WS-VSAM-STATUS
        STOP RUN
    END-IF.
 
MIGRATE-RECORDS.
    PERFORM READ-VSAM-RECORD.
    PERFORM UNTIL WS-VSAM-STATUS = "10"  *> End of file
        ADD 1 TO WS-RECORD-COUNT
        PERFORM CONVERT-RECORD-DATA
        PERFORM INSERT-INTO-DATABASE
        PERFORM READ-VSAM-RECORD
        
        * Progress indicator every 1000 records
        IF FUNCTION MOD(WS-RECORD-COUNT, 1000) = 0
            DISPLAY "Migrated " WS-RECORD-COUNT " records..."
        END-IF
    END-PERFORM.
 
READ-VSAM-RECORD.
    READ CUSTOMER-VSAM
        AT END
            MOVE "10" TO WS-VSAM-STATUS
        NOT AT END
            CONTINUE
    END-READ.
 
CONVERT-RECORD-DATA.
    * Clean and validate customer name
    MOVE FUNCTION TRIM(CUST-NAME) TO WS-CLEAN-NAME.
    INSPECT WS-CLEAN-NAME REPLACING ALL '"' BY "'".
    
    * Clean address
    MOVE FUNCTION TRIM(CUST-ADDRESS) TO WS-CLEAN-ADDRESS.
    INSPECT WS-CLEAN-ADDRESS REPLACING ALL '"' BY "'".
    
    * Convert packed decimal balance
    MOVE CUST-BALANCE TO WS-CONVERTED-BALANCE.
    
    * Convert date from YYYYMMDD to YYYY-MM-DD
    STRING CUST-LAST-UPDATE(1:4) "-"
           CUST-LAST-UPDATE(5:2) "-"
           CUST-LAST-UPDATE(7:2)
           DELIMITED BY SIZE
           INTO WS-FORMATTED-DATE.
 
INSERT-INTO-DATABASE.
    EXEC SQL
        INSERT INTO CUSTOMERS (
            customer_id,
            customer_name,
            address,
            phone,
            email,
            balance,
            last_update,
            status
        ) VALUES (
            :CUST-ID,
            :WS-CLEAN-NAME,
            :WS-CLEAN-ADDRESS,
            :CUST-PHONE,
            :CUST-EMAIL,
            :WS-CONVERTED-BALANCE,
            :WS-FORMATTED-DATE,
            :CUST-STATUS
        )
    END-EXEC.
    
    IF SQLCODE NOT = 0
        ADD 1 TO WS-ERROR-COUNT
        DISPLAY "Insert failed for customer " CUST-ID 
                " - SQLCODE: " SQLCODE
    END-IF.
 
CLOSE-FILES.
    CLOSE CUSTOMER-VSAM.
    EXEC SQL DISCONNECT END-EXEC.
 
GENERATE-MIGRATION-REPORT.
    DISPLAY "=== MIGRATION COMPLETED ===".
    DISPLAY "Total records processed: " WS-RECORD-COUNT.
    DISPLAY "Successful migrations: " 
            (WS-RECORD-COUNT - WS-ERROR-COUNT).
    DISPLAY "Failed migrations: " WS-ERROR-COUNT.
    
    IF WS-ERROR-COUNT = 0
        DISPLAY "Migration completed successfully!"
    ELSE
        DISPLAY "Migration completed with errors. Check logs."
    END-IF.

Copybook to Schema Converter

Copybooks are reusable code modules in COBOL. Converting them to modern schema formats enables better integration with contemporary systems.

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
IDENTIFICATION DIVISION.
PROGRAM-ID. COPYBOOK-SCHEMA-CONVERTER.
 
* Converts COBOL copybooks to JSON Schema, XML Schema, or SQL DDL
* Supports nested structures, arrays, and complex data types
 
DATA DIVISION.
WORKING-STORAGE SECTION.
 
01  WS-OUTPUT-FORMAT      PIC X(10) VALUE "JSON".  *> JSON, XML, SQL
01  WS-COPYBOOK-LINE      PIC X(132).
01  WS-SCHEMA-OUTPUT      PIC X(50000).
01  WS-CURRENT-LEVEL      PIC 99.
01  WS-FIELD-NAME         PIC X(30).
01  WS-FIELD-TYPE         PIC X(20).
01  WS-FIELD-LENGTH       PIC 9(5).
01  WS-DECIMAL-PLACES     PIC 9(2).
 
01  WS-CONVERSION-MAP.
    05  COBOL-TYPES OCCURS 20 TIMES.
        10  COBOL-PIC       PIC X(20).
        10  JSON-TYPE       PIC X(20).
        10  SQL-TYPE        PIC X(30).
        10  XML-TYPE        PIC X(20).
 
PROCEDURE DIVISION.
MAIN-CONVERSION.
    PERFORM INITIALIZE-TYPE-MAPPINGS.
    PERFORM PROCESS-COPYBOOK.
    PERFORM GENERATE-SCHEMA.
    STOP RUN.
 
INITIALIZE-TYPE-MAPPINGS.
    * Define type mappings for different target formats
    MOVE "9" TO COBOL-PIC(1).
    MOVE "integer" TO JSON-TYPE(1).
    MOVE "INTEGER" TO SQL-TYPE(1).
    MOVE "xs:int" TO XML-TYPE(1).
    
    MOVE "X" TO COBOL-PIC(2).
    MOVE "string" TO JSON-TYPE(2).
    MOVE "VARCHAR" TO SQL-TYPE(2).
    MOVE "xs:string" TO XML-TYPE(2).
    
    MOVE "S9" TO COBOL-PIC(3).
    MOVE "integer" TO JSON-TYPE(3).
    MOVE "BIGINT" TO SQL-TYPE(3).
    MOVE "xs:long" TO XML-TYPE(3).
    
    MOVE "9V99" TO COBOL-PIC(4).
    MOVE "number" TO JSON-TYPE(4).
    MOVE "DECIMAL" TO SQL-TYPE(4).
    MOVE "xs:decimal" TO XML-TYPE(4).
 
PROCESS-COPYBOOK.
    * Read and parse COBOL copybook structure
    * This is a simplified example - real implementation would
    * need full COBOL syntax parsing
    
    MOVE "01  CUSTOMER-RECORD." TO WS-COPYBOOK-LINE.
    PERFORM PARSE-COPYBOOK-LINE.
    
    MOVE "    05  CUST-ID         PIC 9(10)." TO WS-COPYBOOK-LINE.
    PERFORM PARSE-COPYBOOK-LINE.
    
    MOVE "    05  CUST-NAME       PIC X(50)." TO WS-COPYBOOK-LINE.
    PERFORM PARSE-COPYBOOK-LINE.
    
    MOVE "    05  CUST-BALANCE    PIC 9(8)V99." TO WS-COPYBOOK-LINE.
    PERFORM PARSE-COPYBOOK-LINE.
 
PARSE-COPYBOOK-LINE.
    * Extract level, field name, and data type from copybook line
    * This is a simplified parser - production version would be more robust
    
    IF WS-COPYBOOK-LINE(8:2) = "01"
        MOVE 1 TO WS-CURRENT-LEVEL
    ELSE IF WS-COPYBOOK-LINE(8:2) = "05"
        MOVE 5 TO WS-CURRENT-LEVEL
    END-IF.
    
    * Extract field name (between level and PIC)
    UNSTRING WS-COPYBOOK-LINE DELIMITED BY SPACE
        INTO WS-CURRENT-LEVEL WS-FIELD-NAME WS-FIELD-TYPE.
 
GENERATE-SCHEMA.
    EVALUATE WS-OUTPUT-FORMAT
        WHEN "JSON"
            PERFORM GENERATE-JSON-SCHEMA
        WHEN "XML"
            PERFORM GENERATE-XML-SCHEMA
        WHEN "SQL"
            PERFORM GENERATE-SQL-DDL
    END-EVALUATE.
 
GENERATE-JSON-SCHEMA.
    STRING 
        "{"
        '"$schema": "https://json-schema.org/draft/2020-12/schema",'
        '"type": "object",'
        '"title": "Customer Record Schema",'
        '"properties": {'
        '"customerId": {'
        '"type": "integer",'
        '"minimum": 0,'
        '"maximum": 9999999999'
        "},"
        '"customerName": {'
        '"type": "string",'
        '"maxLength": 50'
        "},"
        '"customerBalance": {'
        '"type": "number",'
        '"multipleOf": 0.01'
        "}"
        "},"
        '"required": ["customerId", "customerName"]'
        "}"
        DELIMITED BY SIZE
        INTO WS-SCHEMA-OUTPUT.
    
    DISPLAY "Generated JSON Schema:".
    DISPLAY WS-SCHEMA-OUTPUT.
 
GENERATE-XML-SCHEMA.
    STRING
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        ""
        DELIMITED BY SIZE
        INTO WS-SCHEMA-OUTPUT.
    
    DISPLAY "Generated XML Schema:".
    DISPLAY WS-SCHEMA-OUTPUT.
 
GENERATE-SQL-DDL.
    STRING
        "CREATE TABLE customer_record ("
        "    customer_id BIGINT PRIMARY KEY,"
        "    customer_name VARCHAR(50) NOT NULL,"
        "    customer_balance DECIMAL(10,2),"
        "    created_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,"
        "    updated_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP"
        ");"
        DELIMITED BY SIZE
        INTO WS-SCHEMA-OUTPUT.
    
    DISPLAY "Generated SQL DDL:".
    DISPLAY WS-SCHEMA-OUTPUT.

Refactoring COBOL Code

Code refactoring involves restructuring existing COBOL programs to improve readability, maintainability, and performance while preserving functionality. Modern refactoring techniques can dramatically improve code quality and reduce technical debt.

Modularization Techniques

Before: Monolithic Structure

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
IDENTIFICATION DIVISION.
PROGRAM-ID. LEGACY-MONOLITH.
 
* 5000+ line monolithic program
* Multiple responsibilities mixed together
* Difficult to maintain and test
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    * Customer validation mixed with business logic
    IF CUST-ID = SPACES OR CUST-ID = ZEROS
        DISPLAY "Invalid customer ID"
        GO TO END-PROGRAM
    END-IF.
    
    * Database access mixed with calculations
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer not found"
            GO TO END-PROGRAM
    END-READ.
    
    * Business calculation mixed with formatting
    COMPUTE TOTAL-AMOUNT = ITEM-PRICE * QUANTITY.
    ADD TAX-RATE TO TOTAL-AMOUNT.
    MULTIPLY TOTAL-AMOUNT BY DISCOUNT-FACTOR.
    MOVE TOTAL-AMOUNT TO DISPLAY-AMOUNT.
    
    * Output formatting mixed with business logic
    STRING "$" DELIMITED BY SIZE
           DISPLAY-AMOUNT DELIMITED BY SIZE
           INTO FORMATTED-AMOUNT.
    DISPLAY FORMATTED-AMOUNT.
    
END-PROGRAM.
    STOP RUN.

After: Modular Structure

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
IDENTIFICATION DIVISION.
PROGRAM-ID. REFACTORED-MODULAR.
 
* Modular program with clear separation of concerns
* Each function has single responsibility
* Easier to test and maintain
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    PERFORM VALIDATE-INPUT-DATA.
    IF WS-VALIDATION-PASSED
        PERFORM RETRIEVE-CUSTOMER-DATA
        IF WS-CUSTOMER-FOUND
            PERFORM CALCULATE-ORDER-TOTAL
            PERFORM FORMAT-OUTPUT
            PERFORM DISPLAY-RESULTS
        ELSE
            PERFORM HANDLE-CUSTOMER-NOT-FOUND
        END-IF
    ELSE
        PERFORM HANDLE-INVALID-INPUT
    END-IF.
    STOP RUN.
 
VALIDATE-INPUT-DATA.
    * Single responsibility: input validation
    MOVE "Y" TO WS-VALIDATION-PASSED.
    
    IF CUST-ID = SPACES OR CUST-ID = ZEROS
        MOVE "N" TO WS-VALIDATION-PASSED
        MOVE "Invalid customer ID" TO WS-ERROR-MESSAGE
    END-IF.
    
    IF QUANTITY <= 0
        MOVE "N" TO WS-VALIDATION-PASSED
        MOVE "Invalid quantity" TO WS-ERROR-MESSAGE
    END-IF.
 
RETRIEVE-CUSTOMER-DATA.
    * Single responsibility: data access
    READ CUSTOMER-FILE
        INVALID KEY
            MOVE "N" TO WS-CUSTOMER-FOUND
        NOT INVALID KEY
            MOVE "Y" TO WS-CUSTOMER-FOUND
    END-READ.
 
CALCULATE-ORDER-TOTAL.
    * Single responsibility: business calculations
    CALL "CALCULATE-SUBTOTAL" USING
        ITEM-PRICE
        QUANTITY
        WS-SUBTOTAL.
    
    CALL "APPLY-TAX" USING
        WS-SUBTOTAL
        TAX-RATE
        WS-TAX-AMOUNT.
    
    CALL "APPLY-DISCOUNT" USING
        WS-SUBTOTAL
        CUSTOMER-DISCOUNT-RATE
        WS-DISCOUNT-AMOUNT.
    
    COMPUTE TOTAL-AMOUNT = 
        WS-SUBTOTAL + WS-TAX-AMOUNT - WS-DISCOUNT-AMOUNT.
 
FORMAT-OUTPUT.
    * Single responsibility: output formatting
    CALL "FORMAT-CURRENCY" USING
        TOTAL-AMOUNT
        WS-FORMATTED-AMOUNT.
 
DISPLAY-RESULTS.
    * Single responsibility: output display
    DISPLAY "Order Total: " WS-FORMATTED-AMOUNT.

Automated Refactoring Tools

COBOL Refactoring Engine

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
IDENTIFICATION DIVISION.
PROGRAM-ID. COBOL-REFACTOR-ENGINE.
 
* Automated COBOL code refactoring tool
* Identifies anti-patterns and suggests improvements
* Generates refactored code with improved structure
 
DATA DIVISION.
WORKING-STORAGE SECTION.
 
01  WS-REFACTORING-RULES.
    05  RULE-DEFINITIONS OCCURS 50 TIMES.
        10  RULE-ID           PIC 9(3).
        10  RULE-NAME         PIC X(50).
        10  RULE-PATTERN      PIC X(200).
        10  RULE-REPLACEMENT  PIC X(200).
        10  RULE-SEVERITY     PIC X(10).
 
01  WS-CODE-ANALYSIS.
    05  TOTAL-LINES         PIC 9(8).
    05  GOTO-STATEMENTS     PIC 9(5).
    05  LARGE-PARAGRAPHS    PIC 9(5).
    05  DEEP-NESTING        PIC 9(3).
    05  CODE-DUPLICATION    PIC 9(5).
    05  MAGIC-NUMBERS       PIC 9(5).
 
01  WS-REFACTORING-SUGGESTIONS.
    05  SUGGESTION-COUNT    PIC 9(3).
    05  SUGGESTIONS OCCURS 100 TIMES.
        10  SUGGESTION-TYPE    PIC X(30).
        10  LINE-NUMBER        PIC 9(6).
        10  DESCRIPTION        PIC X(100).
        10  RECOMMENDED-ACTION PIC X(200).
 
PROCEDURE DIVISION.
MAIN-REFACTORING.
    PERFORM INITIALIZE-REFACTORING-RULES.
    PERFORM ANALYZE-SOURCE-CODE.
    PERFORM IDENTIFY-REFACTORING-OPPORTUNITIES.
    PERFORM GENERATE-REFACTORING-REPORT.
    PERFORM APPLY-AUTOMATIC-REFACTORINGS.
    STOP RUN.
 
INITIALIZE-REFACTORING-RULES.
    * Rule 1: Eliminate GO TO statements
    MOVE 1 TO RULE-ID(1).
    MOVE "Eliminate GO TO" TO RULE-NAME(1).
    MOVE "GO TO paragraph-name" TO RULE-PATTERN(1).
    MOVE "PERFORM paragraph-name" TO RULE-REPLACEMENT(1).
    MOVE "HIGH" TO RULE-SEVERITY(1).
    
    * Rule 2: Extract magic numbers
    MOVE 2 TO RULE-ID(2).
    MOVE "Extract Magic Numbers" TO RULE-NAME(2).
    MOVE "literal-number" TO RULE-PATTERN(2).
    MOVE "named-constant" TO RULE-REPLACEMENT(2).
    MOVE "MEDIUM" TO RULE-SEVERITY(2).
    
    * Rule 3: Break down large paragraphs
    MOVE 3 TO RULE-ID(3).
    MOVE "Split Large Paragraphs" TO RULE-NAME(3).
    MOVE "paragraph > 50 lines" TO RULE-PATTERN(3).
    MOVE "multiple smaller paragraphs" TO RULE-REPLACEMENT(3).
    MOVE "HIGH" TO RULE-SEVERITY(3).
 
ANALYZE-SOURCE-CODE.
    * Analyze source code for anti-patterns and metrics
    PERFORM COUNT-CODE-METRICS.
    PERFORM DETECT-ANTI-PATTERNS.
    PERFORM CALCULATE-COMPLEXITY-SCORE.
 
COUNT-CODE-METRICS.
    * Count various code metrics
    MOVE 2500 TO TOTAL-LINES.
    MOVE 15 TO GOTO-STATEMENTS.
    MOVE 8 TO LARGE-PARAGRAPHS.
    MOVE 4 TO DEEP-NESTING.
    MOVE 25 TO CODE-DUPLICATION.
    MOVE 42 TO MAGIC-NUMBERS.
 
DETECT-ANTI-PATTERNS.
    * Detect common COBOL anti-patterns
    IF GOTO-STATEMENTS > 0
        ADD 1 TO SUGGESTION-COUNT
        MOVE "Anti-Pattern" TO SUGGESTION-TYPE(SUGGESTION-COUNT)
        MOVE "GO TO statements detected" 
             TO DESCRIPTION(SUGGESTION-COUNT)
        MOVE "Replace with PERFORM statements for better structure"
             TO RECOMMENDED-ACTION(SUGGESTION-COUNT)
    END-IF.
    
    IF LARGE-PARAGRAPHS > 5
        ADD 1 TO SUGGESTION-COUNT
        MOVE "Structure" TO SUGGESTION-TYPE(SUGGESTION-COUNT)
        MOVE "Large paragraphs detected"
             TO DESCRIPTION(SUGGESTION-COUNT)
        MOVE "Break into smaller, focused paragraphs"
             TO RECOMMENDED-ACTION(SUGGESTION-COUNT)
    END-IF.
    
    IF MAGIC-NUMBERS > 20
        ADD 1 TO SUGGESTION-COUNT
        MOVE "Maintainability" TO SUGGESTION-TYPE(SUGGESTION-COUNT)
        MOVE "Magic numbers detected"
             TO DESCRIPTION(SUGGESTION-COUNT)
        MOVE "Replace with named constants"
             TO RECOMMENDED-ACTION(SUGGESTION-COUNT)
    END-IF.
 
GENERATE-REFACTORING-REPORT.
    DISPLAY "=== COBOL REFACTORING ANALYSIS ===".
    DISPLAY "Total Lines of Code: " TOTAL-LINES.
    DISPLAY "Code Quality Issues Found: " SUGGESTION-COUNT.
    DISPLAY " ".
    DISPLAY "=== RECOMMENDATIONS ===".
    
    PERFORM VARYING WS-I FROM 1 BY 1 
            UNTIL WS-I > SUGGESTION-COUNT
        DISPLAY WS-I ". " SUGGESTION-TYPE(WS-I) 
                ": " DESCRIPTION(WS-I)
        DISPLAY "   Action: " RECOMMENDED-ACTION(WS-I)
        DISPLAY " "
    END-PERFORM.
 
APPLY-AUTOMATIC-REFACTORINGS.
    * Apply safe automatic refactorings
    PERFORM REPLACE-GOTO-WITH-PERFORM.
    PERFORM EXTRACT-NAMED-CONSTANTS.
    PERFORM STANDARDIZE-NAMING-CONVENTIONS.
    
    DISPLAY "Automatic refactorings applied successfully.".
 
REPLACE-GOTO-WITH-PERFORM.
    * Automatically replace simple GO TO with PERFORM
    DISPLAY "Replacing GO TO statements with PERFORM...".
    * Implementation would parse and modify source code
 
EXTRACT-NAMED-CONSTANTS.
    * Extract literal values into named constants
    DISPLAY "Extracting magic numbers into named constants...".
    * Implementation would identify and extract literals
 
STANDARDIZE-NAMING-CONVENTIONS.
    * Apply consistent naming conventions
    DISPLAY "Standardizing naming conventions...".
    * Implementation would rename variables consistently

Integration with Modern Languages

Modern COBOL integration involves creating bridges between legacy COBOL systems and contemporary technologies through APIs, message queues, and microservices architectures. This enables gradual modernization while preserving critical business logic.

COBOL-Java Integration

COBOL Service

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
IDENTIFICATION DIVISION.
PROGRAM-ID. CUSTOMER-SERVICE.
 
* COBOL business logic service
* Called from Java via JNI (Java Native Interface)
* Maintains core business rules in COBOL
 
DATA DIVISION.
LINKAGE SECTION.
01  LS-CUSTOMER-ID       PIC 9(10).
01  LS-CUSTOMER-DATA.
    05  LS-CUST-NAME     PIC X(50).
    05  LS-CUST-BALANCE  PIC S9(11)V99 COMP-3.
    05  LS-CUST-STATUS   PIC X(10).
    05  LS-CREDIT-LIMIT  PIC S9(9)V99 COMP-3.
01  LS-RETURN-CODE       PIC 9(2).
 
WORKING-STORAGE SECTION.
01  WS-BUSINESS-RULES.
    05  MIN-BALANCE      PIC S9(9)V99 VALUE -1000.00.
    05  MAX-CREDIT-LIMIT PIC S9(9)V99 VALUE 50000.00.
    05  VIP-THRESHOLD    PIC S9(9)V99 VALUE 10000.00.
 
PROCEDURE DIVISION USING LS-CUSTOMER-ID 
                        LS-CUSTOMER-DATA
                        LS-RETURN-CODE.
 
MAIN-SERVICE.
    PERFORM VALIDATE-CUSTOMER-ID.
    IF LS-RETURN-CODE = 0
        PERFORM RETRIEVE-CUSTOMER-DATA
        IF LS-RETURN-CODE = 0
            PERFORM APPLY-BUSINESS-RULES
        END-IF
    END-IF.
    GOBACK.
 
VALIDATE-CUSTOMER-ID.
    IF LS-CUSTOMER-ID = 0 OR LS-CUSTOMER-ID > 9999999999
        MOVE 99 TO LS-RETURN-CODE
    ELSE
        MOVE 0 TO LS-RETURN-CODE
    END-IF.
 
RETRIEVE-CUSTOMER-DATA.
    * Simulate database access
    * In reality, this would access VSAM, DB2, etc.
    EVALUATE LS-CUSTOMER-ID
        WHEN 12345
            MOVE "JOHN SMITH" TO LS-CUST-NAME
            MOVE 5000.00 TO LS-CUST-BALANCE
            MOVE "ACTIVE" TO LS-CUST-STATUS
            MOVE 15000.00 TO LS-CREDIT-LIMIT
        WHEN OTHER
            MOVE 01 TO LS-RETURN-CODE
    END-EVALUATE.
 
APPLY-BUSINESS-RULES.
    * Apply COBOL-based business logic
    IF LS-CUST-BALANCE < MIN-BALANCE
        MOVE "SUSPENDED" TO LS-CUST-STATUS
    END-IF.
    
    IF LS-CUST-BALANCE > VIP-THRESHOLD
        MOVE "VIP" TO LS-CUST-STATUS
        COMPUTE LS-CREDIT-LIMIT = LS-CREDIT-LIMIT * 1.5
    END-IF.
    
    IF LS-CREDIT-LIMIT > MAX-CREDIT-LIMIT
        MOVE MAX-CREDIT-LIMIT TO LS-CREDIT-LIMIT
    END-IF.

Java Integration Layer

java

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
public class CustomerServiceIntegration {
    
    // Load native COBOL library
    static {
        System.loadLibrary("customerservice");
    }
    
    // Native method declaration for COBOL program
    private native int callCobolCustomerService(
        long customerId,
        CustomerData customerData
    );
    
    /**
     * Customer data structure matching COBOL linkage
     */
    public static class CustomerData {
        public String customerName;
        public double customerBalance;
        public String customerStatus;
        public double creditLimit;
        
        // Constructor
        public CustomerData() {
            this.customerName = "";
            this.customerBalance = 0.0;
            this.customerStatus = "";
            this.creditLimit = 0.0;
        }
    }
    
    /**
     * Business service method that calls COBOL logic
     */
    public CustomerData getCustomerWithBusinessRules(long customerId) 
            throws CustomerServiceException {
        
        CustomerData customerData = new CustomerData();
        
        try {
            // Call COBOL business logic
            int returnCode = callCobolCustomerService(customerId, customerData);
            
            if (returnCode != 0) {
                throw new CustomerServiceException(
                    "COBOL service returned error code: " + returnCode);
            }
            
            return customerData;
            
        } catch (Exception e) {
            throw new CustomerServiceException(
                "Failed to call COBOL service: " + e.getMessage(), e);
        }
    }
    
    /**
     * REST API endpoint using Spring Boot
     */
    @RestController
    @RequestMapping("/api/customers")
    public class CustomerController {
        
        @Autowired
        private CustomerServiceIntegration cobolService;
        
        @GetMapping("/{customerId}")
        public ResponseEntity getCustomer(
                @PathVariable long customerId) {
            
            try {
                CustomerData data = cobolService
                    .getCustomerWithBusinessRules(customerId);
                
                CustomerResponse response = new CustomerResponse();
                response.setCustomerId(customerId);
                response.setName(data.customerName.trim());
                response.setBalance(data.customerBalance);
                response.setStatus(data.customerStatus.trim());
                response.setCreditLimit(data.creditLimit);
                
                return ResponseEntity.ok(response);
                
            } catch (CustomerServiceException e) {
                return ResponseEntity.badRequest()
                    .body(new ErrorResponse(e.getMessage()));
            }
        }
    }
    
    /**
     * Microservice communication using message queues
     */
    @Service
    public class CustomerEventService {
        
        @Autowired
        private CustomerServiceIntegration cobolService;
        
        @Autowired
        private RabbitTemplate rabbitTemplate;
        
        @RabbitListener(queues = "customer.updates")
        public void handleCustomerUpdate(CustomerUpdateEvent event) {
            
            try {
                // Process with COBOL business logic
                CustomerData data = cobolService
                    .getCustomerWithBusinessRules(event.getCustomerId());
                
                // Publish result to other microservices
                CustomerUpdatedEvent result = new CustomerUpdatedEvent();
                result.setCustomerId(event.getCustomerId());
                result.setUpdatedData(data);
                result.setTimestamp(LocalDateTime.now());
                
                rabbitTemplate.convertAndSend(
                    "customer.events", 
                    "customer.updated", 
                    result
                );
                
            } catch (Exception e) {
                // Handle error and send to dead letter queue
                rabbitTemplate.convertAndSend(
                    "customer.dlq", 
                    event
                );
            }
        }
    }
}

COBOL-Python Integration

Python API Gateway for COBOL Services

python

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
"""
COBOL-Python Integration using FastAPI
Provides REST API gateway to legacy COBOL business logic
Supports async processing and modern API patterns
"""
 
import asyncio
import subprocess
import json
from typing import Optional, Dict, Any
from datetime import datetime
from fastapi import FastAPI, HTTPException, BackgroundTasks
from pydantic import BaseModel
import redis
import logging
 
# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
 
app = FastAPI(
    title="COBOL Legacy Integration API",
    description="Modern API gateway for COBOL business services",
    version="1.0.0"
)
 
# Redis for caching and async job tracking
redis_client = redis.Redis(host='localhost', port=6379, db=0)
 
class CustomerRequest(BaseModel):
    customer_id: int
    operation: str = "GET_CUSTOMER"
    
class CustomerResponse(BaseModel):
    customer_id: int
    name: str
    balance: float
    status: str
    credit_limit: float
    last_updated: datetime
 
class CobolJobStatus(BaseModel):
    job_id: str
    status: str  # PENDING, RUNNING, COMPLETED, FAILED
    result: Optional[Dict[Any, Any]] = None
    error_message: Optional[str] = None
    created_at: datetime
    completed_at: Optional[datetime] = None
 
class CobolIntegrationService:
    """Service class for COBOL integration"""
    
    def __init__(self):
        self.cobol_program_path = "/opt/cobol/bin/"
        self.data_exchange_path = "/tmp/cobol_exchange/"
    
    async def call_cobol_program(self, program_name: str, input_data: Dict) -> Dict:
        """
        Call COBOL program asynchronously
        Uses file-based data exchange for complex data structures
        """
        try:
            # Generate unique job ID
            job_id = f"cobol_{datetime.now().strftime('%Y%m%d_%H%M%S_%f')}"
            
            # Prepare input file
            input_file = f"{self.data_exchange_path}{job_id}_input.json"
            output_file = f"{self.data_exchange_path}{job_id}_output.json"
            
            with open(input_file, 'w') as f:
                json.dump(input_data, f)
            
            # Execute COBOL program
            cmd = [
                f"{self.cobol_program_path}{program_name}",
                input_file,
                output_file
            ]
            
            process = await asyncio.create_subprocess_exec(
                *cmd,
                stdout=asyncio.subprocess.PIPE,
                stderr=asyncio.subprocess.PIPE
            )
            
            stdout, stderr = await process.communicate()
            
            if process.returncode != 0:
                error_msg = stderr.decode() if stderr else "Unknown COBOL error"
                logger.error(f"COBOL program failed: {error_msg}")
                raise Exception(f"COBOL execution failed: {error_msg}")
            
            # Read output
            with open(output_file, 'r') as f:
                result = json.load(f)
            
            # Cleanup temporary files
            import os
            os.remove(input_file)
            os.remove(output_file)
            
            return result
            
        except Exception as e:
            logger.error(f"COBOL integration error: {str(e)}")
            raise
 
cobol_service = CobolIntegrationService()
 
@app.post("/api/customers/{customer_id}/process")
async def process_customer_sync(
    customer_id: int, 
    request: CustomerRequest
) -> CustomerResponse:
    """
    Synchronous COBOL processing
    For operations that need immediate response
    """
    try:
        # Prepare input for COBOL program
        cobol_input = {
            "customer_id": customer_id,
            "operation": request.operation,
            "timestamp": datetime.now().isoformat()
        }
        
        # Call COBOL business logic
        result = await cobol_service.call_cobol_program(
            "CUSTOMER-SERVICE", 
            cobol_input
        )
        
        if result.get("return_code") != 0:
            raise HTTPException(
                status_code=400,
                detail=f"COBOL business logic error: {result.get('error_message')}"
            )
        
        # Transform COBOL output to API response
        return CustomerResponse(
            customer_id=customer_id,
            name=result["customer_name"].strip(),
            balance=result["customer_balance"],
            status=result["customer_status"].strip(),
            credit_limit=result["credit_limit"],
            last_updated=datetime.fromisoformat(result["last_updated"])
        )
        
    except Exception as e:
        logger.error(f"Customer processing error: {str(e)}")
        raise HTTPException(status_code=500, detail=str(e))
 
@app.post("/api/batch/customers/process")
async def process_customers_batch(
    customer_ids: list[int],
    background_tasks: BackgroundTasks
) -> Dict[str, str]:
    """
    Asynchronous batch processing
    For large datasets that need background processing
    """
    job_id = f"batch_{datetime.now().strftime('%Y%m%d_%H%M%S_%f')}"
    
    # Store job status in Redis
    job_status = CobolJobStatus(
        job_id=job_id,
        status="PENDING",
        created_at=datetime.now()
    )
    
    redis_client.setex(
        f"job:{job_id}", 
        3600,  # 1 hour expiry
        job_status.model_dump_json()
    )
    
    # Start background processing
    background_tasks.add_task(
        process_batch_async, 
        job_id, 
        customer_ids
    )
    
    return {"job_id": job_id, "status": "PENDING"}
 
async def process_batch_async(job_id: str, customer_ids: list[int]):
    """Background task for batch processing"""
    try:
        # Update job status
        job_status = CobolJobStatus(
            job_id=job_id,
            status="RUNNING",
            created_at=datetime.now()
        )
        redis_client.setex(f"job:{job_id}", 3600, job_status.model_dump_json())
        
        results = []
        for customer_id in customer_ids:
            try:
                cobol_input = {
                    "customer_id": customer_id,
                    "operation": "BATCH_PROCESS"
                }
                
                result = await cobol_service.call_cobol_program(
                    "BATCH-CUSTOMER-SERVICE", 
                    cobol_input
                )
                
                results.append({
                    "customer_id": customer_id,
                    "status": "SUCCESS",
                    "data": result
                })
                
            except Exception as e:
                results.append({
                    "customer_id": customer_id,
                    "status": "ERROR",
                    "error": str(e)
                })
        
        # Update job with results
        job_status = CobolJobStatus(
            job_id=job_id,
            status="COMPLETED",
            result={"processed_customers": results},
            created_at=datetime.now(),
            completed_at=datetime.now()
        )
        redis_client.setex(f"job:{job_id}", 3600, job_status.model_dump_json())
        
    except Exception as e:
        # Update job with error
        job_status = CobolJobStatus(
            job_id=job_id,
            status="FAILED",
            error_message=str(e),
            created_at=datetime.now(),
            completed_at=datetime.now()
        )
        redis_client.setex(f"job:{job_id}", 3600, job_status.model_dump_json())
 
@app.get("/api/jobs/{job_id}/status")
async def get_job_status(job_id: str) -> CobolJobStatus:
    """Get status of async job"""
    job_data = redis_client.get(f"job:{job_id}")
    
    if not job_data:
        raise HTTPException(status_code=404, detail="Job not found")
    
    return CobolJobStatus.model_validate_json(job_data)
 
@app.get("/health")
async def health_check():
    """Health check endpoint"""
    return {
        "status": "healthy",
        "timestamp": datetime.now().isoformat(),
        "cobol_integration": "active"
    }
 
if __name__ == "__main__":
    import uvicorn
    uvicorn.run(
        app, 
        host="0.0.0.0", 
        port=8000,
        log_level="info"
    )

Cloud Deployment Strategies

Moving COBOL applications to the cloud requires careful planning and specialized strategies. Cloud deployment can reduce infrastructure costs, improve scalability, and enable better integration with modern services while maintaining the reliability and performance of legacy systems.

Containerization Approach

Dockerfile for COBOL Applications

dockerfile

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
80
81
82
83
84
85
86
87
# Multi-stage Docker build for COBOL applications
# Stage 1: Build environment with COBOL compiler
FROM ubuntu:22.04 AS cobol-builder
 
# Install GnuCOBOL compiler and dependencies
RUN apt-get update && apt-get install -y \
    gnucobol4 \
    build-essential \
    libdb-dev \
    libncurses5-dev \
    libgmp-dev \
    && rm -rf /var/lib/apt/lists/*
 
# Set environment variables for COBOL
ENV COB_CONFIG_DIR=/usr/share/gnucobol/config
ENV COB_COPY_DIR=/usr/share/gnucobol/copy
ENV COB_LIBRARY_PATH=/usr/lib/gnucobol
 
# Create application directory
WORKDIR /app/src
 
# Copy COBOL source files
COPY src/ ./
COPY copybooks/ ./copybooks/
 
# Compile COBOL programs
RUN cobc -x -o customer-service CUSTOMER-SERVICE.cob
RUN cobc -x -o order-processor ORDER-PROCESSOR.cob
RUN cobc -x -o batch-runner BATCH-RUNNER.cob
 
# Stage 2: Runtime environment
FROM ubuntu:22.04 AS cobol-runtime
 
# Install only runtime dependencies
RUN apt-get update && apt-get install -y \
    libcob4 \
    libdb5.3 \
    libncurses5 \
    curl \
    jq \
    && rm -rf /var/lib/apt/lists/*
 
# Create non-root user for security
RUN groupadd -r cobolapp && useradd -r -g cobolapp cobolapp
 
# Create application directories
WORKDIR /app
RUN mkdir -p /app/bin /app/data /app/logs /app/config \
    && chown -R cobolapp:cobolapp /app
 
# Copy compiled programs from builder stage
COPY --from=cobol-builder /app/src/customer-service /app/bin/
COPY --from=cobol-builder /app/src/order-processor /app/bin/
COPY --from=cobol-builder /app/src/batch-runner /app/bin/
 
# Copy configuration files
COPY config/ /app/config/
COPY scripts/ /app/scripts/
 
# Set permissions
RUN chmod +x /app/bin/* /app/scripts/*
RUN chown -R cobolapp:cobolapp /app
 
# Create health check script
RUN echo '#!/bin/bash\n\
echo "COBOL Application Health Check"\n\
/app/bin/customer-service --health-check\n\
exit $?' > /app/health-check.sh \
    && chmod +x /app/health-check.sh
 
# Switch to non-root user
USER cobolapp
 
# Set environment variables
ENV COBOL_APP_HOME=/app
ENV COBOL_DATA_DIR=/app/data
ENV COBOL_LOG_DIR=/app/logs
 
# Health check
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
    CMD /app/health-check.sh
 
# Expose application port
EXPOSE 8080
 
# Default command
CMD ["/app/scripts/start-cobol-service.sh"]

Kubernetes Deployment

yaml

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
# Kubernetes deployment for COBOL microservice
apiVersion: apps/v1
kind: Deployment
metadata:
  name: cobol-customer-service
  labels:
    app: cobol-customer-service
    version: v1.0
spec:
  replicas: 3
  selector:
    matchLabels:
      app: cobol-customer-service
  template:
    metadata:
      labels:
        app: cobol-customer-service
        version: v1.0
    spec:
      containers:
      - name: cobol-service
        image: company/cobol-customer-service:1.0
        ports:
        - containerPort: 8080
          name: http
        env:
        - name: ENVIRONMENT
          value: "production"
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: cobol-secrets
              key: database-url
        - name: LOG_LEVEL
          value: "INFO"
        
        # Resource limits
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        
        # Health checks
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 3
        
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
          timeoutSeconds: 3
          successThreshold: 1
          failureThreshold: 3
        
        # Volume mounts
        volumeMounts:
        - name: cobol-config
          mountPath: /app/config
          readOnly: true
        - name: cobol-data
          mountPath: /app/data
        - name: cobol-logs
          mountPath: /app/logs
      
      volumes:
      - name: cobol-config
        configMap:
          name: cobol-config
      - name: cobol-data
        persistentVolumeClaim:
          claimName: cobol-data-pvc
      - name: cobol-logs
        emptyDir: {}
      
      # Security context
      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        fsGroup: 1000
 
---
# Service to expose the deployment
apiVersion: v1
kind: Service
metadata:
  name: cobol-customer-service
  labels:
    app: cobol-customer-service
spec:
  type: ClusterIP
  ports:
  - port: 80
    targetPort: 8080
    protocol: TCP
    name: http
  selector:
    app: cobol-customer-service
 
---
# Horizontal Pod Autoscaler
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: cobol-customer-service-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: cobol-customer-service
  minReplicas: 3
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80
 
---
# ConfigMap for COBOL application configuration
apiVersion: v1
kind: ConfigMap
metadata:
  name: cobol-config
data:
  application.conf: |
    # COBOL Application Configuration
    database.pool.size=10
    database.timeout=30
    batch.size=1000
    log.level=INFO
    metrics.enabled=true
  
  runtime.conf: |
    # COBOL Runtime Configuration
    COB_SET_RUNTIME_TRACEFILE=/app/logs/trace.log
    COB_SET_DEBUG=Y
    COB_DISABLE_WARNINGS=N
 
---
# Persistent Volume Claim for data
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cobol-data-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: fast-ssd

Serverless COBOL Functions

AWS Lambda COBOL Function

bash

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
// AWS Lambda custom runtime for COBOL
// bootstrap script for COBOL Lambda function
 
#!/bin/bash
 
# AWS Lambda Custom Runtime for COBOL
# This script bootstraps COBOL programs to run as Lambda functions
 
set -euo pipefail
 
# Environment setup
export LAMBDA_TASK_ROOT="/var/task"
export LAMBDA_RUNTIME_DIR="/var/runtime"
export PATH="$LAMBDA_RUNTIME_DIR:$PATH"
 
# COBOL runtime environment
export COB_LIBRARY_PATH="/opt/cobol/lib"
export COB_CONFIG_DIR="/opt/cobol/config"
 
# Function to handle Lambda runtime API
function get_next_event() {
    local endpoint="http://AWS_LAMBDA_RUNTIME_API/2018-06-01/runtime/invocation/next"
    local response=$(curl -sS -LD "$1" "$endpoint")
    echo "$response"
}
 
function send_response() {
    local request_id="$1"
    local response_body="$2"
    local endpoint="http://AWS_LAMBDA_RUNTIME_API/2018-06-01/runtime/invocation/$request_id/response"
    curl -sS -X POST "$endpoint" -d "$response_body"
}
 
function send_error() {
    local request_id="$1"
    local error_message="$2"
    local endpoint="http://AWS_LAMBDA_RUNTIME_API/2018-06-01/runtime/invocation/$request_id/error"
    local error_payload="{"errorMessage": "$error_message", "errorType": "Runtime.HandlerError"}"
    curl -sS -X POST "$endpoint" -d "$error_payload"
}
 
# Main runtime loop
while true; do
    echo "Waiting for next Lambda event..."
    
    # Get event from Lambda runtime API
    HEADERS="/tmp/headers"
    EVENT_DATA=$(get_next_event "$HEADERS")
    REQUEST_ID=$(grep -i "lambda-runtime-aws-request-id:" "$HEADERS" | cut -d: -f2 | tr -d ' 
')
    
    echo "Processing request ID: $REQUEST_ID"
    
    # Create temporary files for COBOL I/O
    INPUT_FILE="/tmp/lambda_input_$REQUEST_ID.json"
    OUTPUT_FILE="/tmp/lambda_output_$REQUEST_ID.json"
    
    # Write event data to input file
    echo "$EVENT_DATA" > "$INPUT_FILE"
    
    # Execute COBOL program
    if "$LAMBDA_TASK_ROOT/cobol-lambda-handler" "$INPUT_FILE" "$OUTPUT_FILE"; then
        # Read response from output file
        if [ -f "$OUTPUT_FILE" ]; then
            RESPONSE_BODY=$(cat "$OUTPUT_FILE")
            send_response "$REQUEST_ID" "$RESPONSE_BODY"
        else
            send_error "$REQUEST_ID" "COBOL program did not produce output"
        fi
    else
        COBOL_EXIT_CODE=$?
        send_error "$REQUEST_ID" "COBOL program failed with exit code: $COBOL_EXIT_CODE"
    fi
    
    # Cleanup
    rm -f "$INPUT_FILE" "$OUTPUT_FILE" "$HEADERS"
done
 
# COBOL Lambda Handler Program
# COBOL-LAMBDA-HANDLER.cob
 
IDENTIFICATION DIVISION.
PROGRAM-ID. COBOL-LAMBDA-HANDLER.
 
* AWS Lambda handler written in COBOL
* Processes JSON events and returns JSON responses
* Demonstrates serverless COBOL capabilities
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INPUT-FILE ASSIGN TO WS-INPUT-FILENAME
        ORGANIZATION IS LINE SEQUENTIAL.
    SELECT OUTPUT-FILE ASSIGN TO WS-OUTPUT-FILENAME
        ORGANIZATION IS LINE SEQUENTIAL.
 
DATA DIVISION.
FILE SECTION.
FD  INPUT-FILE.
01  INPUT-RECORD    PIC X(4096).
 
FD  OUTPUT-FILE.
01  OUTPUT-RECORD   PIC X(4096).
 
WORKING-STORAGE SECTION.
01  WS-INPUT-FILENAME    PIC X(256).
01  WS-OUTPUT-FILENAME   PIC X(256).
01  WS-JSON-INPUT        PIC X(10000).
01  WS-JSON-OUTPUT       PIC X(10000).
 
* Lambda event processing
01  WS-EVENT-DATA.
    05  EVENT-TYPE       PIC X(50).
    05  CUSTOMER-ID      PIC 9(10).
    05  REQUEST-DATA     PIC X(1000).
 
* Response structure
01  WS-RESPONSE-DATA.
    05  STATUS-CODE      PIC 9(3) VALUE 200.
    05  MESSAGE          PIC X(100).
    05  RESULT-DATA      PIC X(2000).
    05  PROCESSING-TIME  PIC 9(5).
 
PROCEDURE DIVISION.
MAIN-LAMBDA-HANDLER.
    * Get command line arguments (input and output files)
    ACCEPT WS-INPUT-FILENAME FROM COMMAND-LINE.
    ACCEPT WS-OUTPUT-FILENAME FROM COMMAND-LINE.
    
    * Process Lambda event
    PERFORM READ-EVENT-DATA.
    PERFORM PARSE-JSON-EVENT.
    PERFORM PROCESS-BUSINESS-LOGIC.
    PERFORM GENERATE-JSON-RESPONSE.
    PERFORM WRITE-RESPONSE-DATA.
    
    STOP RUN.
 
READ-EVENT-DATA.
    OPEN INPUT INPUT-FILE.
    MOVE SPACES TO WS-JSON-INPUT.
    
    READ INPUT-FILE INTO INPUT-RECORD
        AT END
            DISPLAY "Error: No input data"
            MOVE 400 TO STATUS-CODE
            MOVE "No input data received" TO MESSAGE
    END-READ.
    
    * Concatenate multiple lines if needed
    PERFORM UNTIL INPUT-RECORD = SPACES
        STRING WS-JSON-INPUT DELIMITED BY SPACE
               INPUT-RECORD DELIMITED BY SIZE
               INTO WS-JSON-INPUT
        READ INPUT-FILE INTO INPUT-RECORD
            AT END
                MOVE SPACES TO INPUT-RECORD
        END-READ
    END-PERFORM.
    
    CLOSE INPUT-FILE.
 
PARSE-JSON-EVENT.
    * Simple JSON parsing (in production, use JSON library)
    * Extract event type and customer ID from JSON
    
    * Look for "eventType" field
    UNSTRING WS-JSON-INPUT DELIMITED BY '"eventType":"'
        INTO WS-TEMP-DATA EVENT-TYPE.
    
    * Extract customer ID
    UNSTRING WS-JSON-INPUT DELIMITED BY '"customerId":'
        INTO WS-TEMP-DATA CUSTOMER-ID.
 
PROCESS-BUSINESS-LOGIC.
    * Process based on event type
    EVALUATE EVENT-TYPE
        WHEN "GET_CUSTOMER"
            PERFORM GET-CUSTOMER-LOGIC
        WHEN "UPDATE_CUSTOMER"
            PERFORM UPDATE-CUSTOMER-LOGIC
        WHEN "CALCULATE_INTEREST"
            PERFORM CALCULATE-INTEREST-LOGIC
        WHEN OTHER
            MOVE 400 TO STATUS-CODE
            MOVE "Unknown event type" TO MESSAGE
    END-EVALUATE.
 
GET-CUSTOMER-LOGIC.
    * Simulate customer lookup
    IF CUSTOMER-ID = 12345
        MOVE 200 TO STATUS-CODE
        MOVE "Customer found" TO MESSAGE
        STRING '{"customerId":' CUSTOMER-ID ','
               '"name":"John Smith",'
               '"balance":5000.00,'
               '"status":"ACTIVE"}'
               DELIMITED BY SIZE
               INTO RESULT-DATA
    ELSE
        MOVE 404 TO STATUS-CODE
        MOVE "Customer not found" TO MESSAGE
        MOVE '{"error":"Customer not found"}' TO RESULT-DATA
    END-IF.
 
GENERATE-JSON-RESPONSE.
    * Generate Lambda response in JSON format
    STRING '{'
           '"statusCode":' STATUS-CODE ','
           '"headers":{"Content-Type":"application/json"},'
           '"body":{"message":"' FUNCTION TRIM(MESSAGE) '",'
           '"data":' FUNCTION TRIM(RESULT-DATA) ','
           '"processingTime":' PROCESSING-TIME '}'
           '}'
           DELIMITED BY SIZE
           INTO WS-JSON-OUTPUT.
 
WRITE-RESPONSE-DATA.
    OPEN OUTPUT OUTPUT-FILE.
    MOVE WS-JSON-OUTPUT TO OUTPUT-RECORD.
    WRITE OUTPUT-RECORD.
    CLOSE OUTPUT-FILE.

Modernization Tools and Techniques

Modern COBOL modernization relies on sophisticated tools and techniques that can analyze, transform, and optimize legacy code. These tools help organizations make informed decisions about their modernization strategy and automate much of the transformation process.

Code Analysis and Discovery Tools

Static Analysis Tools

IBM Application Discovery: Comprehensive COBOL code analysis
Micro Focus Enterprise Analyzer: Impact analysis and documentation
CAST Application Intelligence: Technical debt assessment
SonarQube COBOL: Code quality and security analysis
BluePhoenix: Automated modernization platform

Runtime Analysis Tools

IBM Application Performance Analyzer: Runtime behavior analysis
Compuware Topaz: Program flow and data analysis
CA Brightside: Modern development environment
Rocket Software: Legacy system monitoring
BMC AMI: Application performance insights

Custom Modernization Toolkit

COBOL Modernization Assessment Tool

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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
IDENTIFICATION DIVISION.
PROGRAM-ID. MODERNIZATION-TOOLKIT.
 
* Comprehensive COBOL Modernization Assessment Tool
* Analyzes legacy systems for cloud readiness
* Generates modernization roadmap and cost estimates
 
DATA DIVISION.
WORKING-STORAGE SECTION.
 
01  WS-ASSESSMENT-CONFIG.
    05  ANALYSIS-DEPTH      PIC X(10) VALUE "DEEP".
    05  OUTPUT-FORMAT       PIC X(10) VALUE "JSON".
    05  INCLUDE-ESTIMATES   PIC X VALUE "Y".
    05  GENERATE-ROADMAP    PIC X VALUE "Y".
 
01  WS-SYSTEM-INVENTORY.
    05  TOTAL-PROGRAMS      PIC 9(5).
    05  TOTAL-COPYBOOKS     PIC 9(4).
    05  TOTAL-LOC           PIC 9(8).
    05  TOTAL-TABLES        PIC 9(4).
    05  TOTAL-SCREENS       PIC 9(3).
 
01  WS-COMPLEXITY-METRICS.
    05  AVG-CYCLOMATIC      PIC 9(3)V99.
    05  MAX-NESTING-DEPTH   PIC 9(2).
    05  GOTO-DENSITY        PIC 9(3)V99.
    05  COUPLING-INDEX      PIC 9(3)V99.
    05  COHESION-INDEX      PIC 9(3)V99.
 
01  WS-TECHNOLOGY-ANALYSIS.
    05  DATABASE-TYPES OCCURS 10 TIMES.
        10  DB-TYPE         PIC X(20).
        10  DB-USAGE-COUNT  PIC 9(5).
        10  DB-COMPLEXITY   PIC 9(3).
    05  SCREEN-TECHNOLOGIES OCCURS 5 TIMES.
        10  SCREEN-TYPE     PIC X(20).
        10  SCREEN-COUNT    PIC 9(3).
    05  INTEGRATION-POINTS OCCURS 20 TIMES.
        10  INT-TYPE        PIC X(30).
        10  INT-COUNT       PIC 9(3).
        10  INT-COMPLEXITY  PIC 9(3).
 
01  WS-MODERNIZATION-OPTIONS.
    05  STRATEGY-OPTIONS OCCURS 5 TIMES.
        10  STRATEGY-NAME     PIC X(30).
        10  EFFORT-ESTIMATE   PIC 9(5).   *> Person-days
        10  COST-ESTIMATE     PIC 9(8)V99. *> USD
        10  RISK-LEVEL        PIC 9(2).   *> 1-10 scale
        10  BENEFITS-SCORE    PIC 9(2).   *> 1-10 scale
        10  TIMELINE-MONTHS   PIC 9(3).
 
01  WS-CLOUD-READINESS.
    05  READINESS-SCORE     PIC 9(3)V99.
    05  READINESS-FACTORS OCCURS 15 TIMES.
        10  FACTOR-NAME     PIC X(40).
        10  FACTOR-SCORE    PIC 9(2).   *> 1-10
        10  FACTOR-WEIGHT   PIC 9V99.   *> 0.1-1.0
 
01  WS-RECOMMENDATIONS.
    05  RECOMMENDED-STRATEGY PIC X(30).
    05  PRIORITY-PROGRAMS OCCURS 20 TIMES.
        10  PROG-NAME       PIC X(20).
        10  PROG-PRIORITY   PIC X(10).
        10  PROG-APPROACH   PIC X(30).
    05  QUICK-WINS OCCURS 10 TIMES.
        10  QW-DESCRIPTION  PIC X(100).
        10  QW-EFFORT       PIC 9(3).
        10  QW-IMPACT       PIC X(10).
 
PROCEDURE DIVISION.
MAIN-MODERNIZATION-ASSESSMENT.
    PERFORM INITIALIZE-ASSESSMENT.
    PERFORM DISCOVER-SYSTEM-INVENTORY.
    PERFORM ANALYZE-CODE-COMPLEXITY.
    PERFORM ANALYZE-TECHNOLOGY-STACK.
    PERFORM ASSESS-CLOUD-READINESS.
    PERFORM GENERATE-MODERNIZATION-OPTIONS.
    PERFORM CALCULATE-RECOMMENDATIONS.
    PERFORM GENERATE-ASSESSMENT-REPORT.
    STOP RUN.
 
DISCOVER-SYSTEM-INVENTORY.
    * Discover and catalog all COBOL assets
    DISPLAY "Discovering COBOL system inventory...".
    
    * Simulate discovery process
    MOVE 485 TO TOTAL-PROGRAMS.
    MOVE 127 TO TOTAL-COPYBOOKS.
    MOVE 2450000 TO TOTAL-LOC.
    MOVE 89 TO TOTAL-TABLES.
    MOVE 156 TO TOTAL-SCREENS.
    
    DISPLAY "Found " TOTAL-PROGRAMS " COBOL programs".
    DISPLAY "Total lines of code: " TOTAL-LOC.
 
ANALYZE-CODE-COMPLEXITY.
    * Analyze code complexity metrics
    COMPUTE AVG-CYCLOMATIC = TOTAL-LOC / (TOTAL-PROGRAMS * 100).
    MOVE 8 TO MAX-NESTING-DEPTH.
    COMPUTE GOTO-DENSITY = (TOTAL-PROGRAMS * 0.15).
    
    * Calculate coupling and cohesion
    COMPUTE COUPLING-INDEX = 
        (TOTAL-COPYBOOKS / TOTAL-PROGRAMS) * 10.
    COMPUTE COHESION-INDEX = 
        100 - ((TOTAL-LOC / TOTAL-PROGRAMS) / 50).
 
ANALYZE-TECHNOLOGY-STACK.
    * Analyze database technologies
    MOVE "VSAM" TO DB-TYPE(1).
    MOVE 234 TO DB-USAGE-COUNT(1).
    MOVE 8 TO DB-COMPLEXITY(1).
    
    MOVE "DB2" TO DB-TYPE(2).
    MOVE 156 TO DB-USAGE-COUNT(2).
    MOVE 6 TO DB-COMPLEXITY(2).
    
    MOVE "IMS" TO DB-TYPE(3).
    MOVE 89 TO DB-USAGE-COUNT(3).
    MOVE 9 TO DB-COMPLEXITY(3).
    
    * Analyze screen technologies
    MOVE "3270 CICS" TO SCREEN-TYPE(1).
    MOVE 134 TO SCREEN-COUNT(1).
    
    MOVE "Batch Reports" TO SCREEN-TYPE(2).
    MOVE 22 TO SCREEN-COUNT(2).
 
ASSESS-CLOUD-READINESS.
    * Assess cloud migration readiness
    MOVE "State Management" TO FACTOR-NAME(1).
    MOVE 7 TO FACTOR-SCORE(1).
    MOVE 0.9 TO FACTOR-WEIGHT(1).
    
    MOVE "Database Dependencies" TO FACTOR-NAME(2).
    MOVE 5 TO FACTOR-SCORE(2).
    MOVE 0.8 TO FACTOR-WEIGHT(2).
    
    MOVE "Integration Complexity" TO FACTOR-NAME(3).
    MOVE 6 TO FACTOR-SCORE(3).
    MOVE 0.7 TO FACTOR-WEIGHT(3).
    
    MOVE "Security Requirements" TO FACTOR-NAME(4).
    MOVE 8 TO FACTOR-SCORE(4).
    MOVE 0.8 TO FACTOR-WEIGHT(4).
    
    * Calculate weighted readiness score
    COMPUTE READINESS-SCORE = 
        ((FACTOR-SCORE(1) * FACTOR-WEIGHT(1)) +
         (FACTOR-SCORE(2) * FACTOR-WEIGHT(2)) +
         (FACTOR-SCORE(3) * FACTOR-WEIGHT(3)) +
         (FACTOR-SCORE(4) * FACTOR-WEIGHT(4))) / 4 * 10.
 
GENERATE-MODERNIZATION-OPTIONS.
    * Option 1: Rehost (Lift and Shift)
    MOVE "Rehost to Cloud" TO STRATEGY-NAME(1).
    COMPUTE EFFORT-ESTIMATE(1) = TOTAL-LOC / 10000.
    COMPUTE COST-ESTIMATE(1) = EFFORT-ESTIMATE(1) * 800.
    MOVE 3 TO RISK-LEVEL(1).
    MOVE 4 TO BENEFITS-SCORE(1).
    MOVE 6 TO TIMELINE-MONTHS(1).
    
    * Option 2: Replatform
    MOVE "Replatform with Optimization" TO STRATEGY-NAME(2).
    COMPUTE EFFORT-ESTIMATE(2) = TOTAL-LOC / 5000.
    COMPUTE COST-ESTIMATE(2) = EFFORT-ESTIMATE(2) * 1000.
    MOVE 5 TO RISK-LEVEL(2).
    MOVE 6 TO BENEFITS-SCORE(2).
    MOVE 12 TO TIMELINE-MONTHS(2).
    
    * Option 3: Refactor
    MOVE "Refactor to Microservices" TO STRATEGY-NAME(3).
    COMPUTE EFFORT-ESTIMATE(3) = TOTAL-LOC / 2000.
    COMPUTE COST-ESTIMATE(3) = EFFORT-ESTIMATE(3) * 1200.
    MOVE 8 TO RISK-LEVEL(3).
    MOVE 9 TO BENEFITS-SCORE(3).
    MOVE 24 TO TIMELINE-MONTHS(3).
    
    * Option 4: Replace
    MOVE "Replace with Modern Stack" TO STRATEGY-NAME(4).
    COMPUTE EFFORT-ESTIMATE(4) = TOTAL-LOC / 1000.
    COMPUTE COST-ESTIMATE(4) = EFFORT-ESTIMATE(4) * 1500.
    MOVE 9 TO RISK-LEVEL(4).
    MOVE 10 TO BENEFITS-SCORE(4).
    MOVE 36 TO TIMELINE-MONTHS(4).
 
CALCULATE-RECOMMENDATIONS.
    * Calculate best strategy based on multiple factors
    EVALUATE TRUE
        WHEN READINESS-SCORE > 80 AND RISK-LEVEL(3) < 7
            MOVE "Refactor to Microservices" TO RECOMMENDED-STRATEGY
        WHEN READINESS-SCORE > 60
            MOVE "Replatform with Optimization" TO RECOMMENDED-STRATEGY
        WHEN OTHER
            MOVE "Rehost to Cloud" TO RECOMMENDED-STRATEGY
    END-EVALUATE.
    
    * Identify quick wins
    MOVE "Containerize batch jobs" TO QW-DESCRIPTION(1).
    MOVE 15 TO QW-EFFORT(1).
    MOVE "HIGH" TO QW-IMPACT(1).
    
    MOVE "Migrate reports to cloud" TO QW-DESCRIPTION(2).
    MOVE 25 TO QW-EFFORT(2).
    MOVE "MEDIUM" TO QW-IMPACT(2).
    
    MOVE "Implement API gateway" TO QW-DESCRIPTION(3).
    MOVE 40 TO QW-EFFORT(3).
    MOVE "HIGH" TO QW-IMPACT(3).
 
GENERATE-ASSESSMENT-REPORT.
    DISPLAY "=== COBOL MODERNIZATION ASSESSMENT REPORT ===".
    DISPLAY " ".
    DISPLAY "SYSTEM INVENTORY:".
    DISPLAY "  Programs: " TOTAL-PROGRAMS.
    DISPLAY "  Lines of Code: " TOTAL-LOC.
    DISPLAY "  Copybooks: " TOTAL-COPYBOOKS.
    DISPLAY " ".
    DISPLAY "COMPLEXITY ANALYSIS:".
    DISPLAY "  Average Cyclomatic Complexity: " AVG-CYCLOMATIC.
    DISPLAY "  Maximum Nesting Depth: " MAX-NESTING-DEPTH.
    DISPLAY "  GOTO Density: " GOTO-DENSITY "%".
    DISPLAY " ".
    DISPLAY "CLOUD READINESS SCORE: " READINESS-SCORE "/100".
    DISPLAY " ".
    DISPLAY "RECOMMENDED STRATEGY: " RECOMMENDED-STRATEGY.
    DISPLAY " ".
    DISPLAY "MODERNIZATION OPTIONS:".
    PERFORM VARYING WS-I FROM 1 BY 1 UNTIL WS-I > 4
        DISPLAY "  " WS-I ". " STRATEGY-NAME(WS-I)
        DISPLAY "     Effort: " EFFORT-ESTIMATE(WS-I) " days"
        DISPLAY "     Cost: $" COST-ESTIMATE(WS-I)
        DISPLAY "     Risk: " RISK-LEVEL(WS-I) "/10"
        DISPLAY "     Benefits: " BENEFITS-SCORE(WS-I) "/10"
        DISPLAY "     Timeline: " TIMELINE-MONTHS(WS-I) " months"
        DISPLAY " "
    END-PERFORM.
    
    DISPLAY "QUICK WINS:".
    PERFORM VARYING WS-I FROM 1 BY 1 UNTIL WS-I > 3
        DISPLAY "  - " QW-DESCRIPTION(WS-I)
        DISPLAY "    Effort: " QW-EFFORT(WS-I) " days"
        DISPLAY "    Impact: " QW-IMPACT(WS-I)
        DISPLAY " "
    END-PERFORM.

🔧 Practical Exercise

Exercise: Migration Assessment

You have a legacy COBOL system with the following characteristics:

750,000 lines of COBOL code across 200 programs
Heavy use of VSAM files and DB2 databases
50 3270 screen programs for user interaction
15 batch jobs running nightly
Integration with 5 external systems via file transfers

Task: Create a migration assessment using the criteria learned in this tutorial.

Assessment Template:

Calculate complexity score (hint: consider lines per program, database dependencies)
Identify migration challenges (VSAM conversion, screen modernization)
Recommend migration strategy (Rehost, Replatform, Refactor, or Replace)
Estimate effort in person-days
List 3 quick wins for immediate value

📚 Related Concepts

Technical Concepts

Microservices Architecture: Breaking monolithic COBOL into smaller services
API Gateway Pattern: Single entry point for legacy system access
Event-Driven Architecture: Asynchronous communication between systems
Database Modernization: Moving from hierarchical to relational databases
Containerization: Packaging COBOL applications for cloud deployment

Business Concepts

Technical Debt: Cost of maintaining legacy systems
Digital Transformation: Business process modernization
Risk Assessment: Evaluating modernization project risks
ROI Analysis: Return on investment for modernization
Change Management: Managing organizational transformation

🔗 Related Tutorial Pages

Foundation Topics

COBOL Basics - Understanding COBOL fundamentals
Distributed Environments - COBOL on modern platforms
XML/JSON Integration - Modern data format handling

Advanced Topics

Object-Oriented COBOL - Modern programming paradigms
COBOL and SQL - Database integration
Performance Optimization - Improving system efficiency

❓ Frequently Asked Questions

Q: How long does a typical COBOL modernization project take?

Project duration varies significantly based on scope and strategy. Simple rehosting can take 6-12 months, while complete refactoring may require 2-5 years. Most organizations adopt a phased approach, starting with quick wins and gradually modernizing critical components over 3-7 years.

Q: What are the biggest risks in COBOL migration projects?

Key risks include: (1) Business logic loss - decades of embedded business rules may be lost or misunderstood; (2) Data integrity issues - complex data transformations can introduce errors; (3) Performance degradation - modern systems may not match mainframe performance; (4) Skills shortage - limited expertise in both legacy and modern technologies; (5) Integration complexity - existing system dependencies are often more complex than initially understood.

Q: Can COBOL applications run efficiently in the cloud?

Yes, with proper planning. Cloud deployment success depends on application architecture, data access patterns, and modernization approach. Stateless batch processes often migrate successfully, while transaction-heavy applications may require more extensive refactoring. Modern COBOL compilers like GnuCOBOL and Micro Focus support cloud deployment, and containerization enables scalable cloud operations.

Q: What's the difference between MIPS and cloud computing costs?

MIPS (Million Instructions Per Second) pricing on mainframes can cost $3,000-$10,000+ per MIPS annually, with peak usage driving costs higher. Cloud computing offers pay-per-use models, auto-scaling, and typically lower baseline costs. However, cloud migration requires careful capacity planning as "chatty" applications may incur network costs, and poorly optimized cloud applications can exceed mainframe costs.

Q: How do you handle COBOL-specific data types in modern systems?

COBOL's packed decimal (COMP-3), binary (COMP), and display formats require careful mapping. Common strategies include: (1) Creating data transformation layers that convert between COBOL and modern formats; (2) Using middleware that understands COBOL data types; (3) Implementing custom serialization/deserialization logic; (4) Leveraging tools like IBM COBOL-JSON or Micro Focus Data Tools for automatic conversion.

Q: What tools are available for automated COBOL modernization?

Leading tools include: IBM Rational Developer for System z (analysis and transformation), Micro Focus Enterprise Developer (cross-platform development), CAST Software (technical debt analysis), BluePhoenix (automated modernization), Semantic Designs (code transformation), and Modern Systems (cloud migration platform). Most tools require significant configuration and human oversight for complex transformations.

🎯 Key Takeaways

Strategic Assessment is Critical: Thorough analysis of complexity, dependencies, and business value determines the optimal modernization approach
Multiple Migration Paths: Rehost, Replatform, Refactor, and Replace strategies each have specific use cases and trade-offs
Gradual Transformation Works Best: Phased approaches with quick wins provide immediate value while building toward comprehensive modernization
Integration is Key to Success: Modern COBOL systems must integrate seamlessly with contemporary architectures through APIs, microservices, and cloud-native patterns
Skills and Tools are Essential: Success requires both COBOL expertise and modern technology knowledge, supported by appropriate tooling and methodologies
Risk Management is Paramount: Proper testing, data validation, and rollback strategies are essential for mission-critical business systems

COBOL and XML/JSON COBOL Tutorial Complete

COBOL Tutorial

COBOL Migration and Modernization

Key Modernization Drivers

Migrating Legacy COBOL Applications

Migration Strategy Overview

Rehost (Lift & Shift)

Replatform

Refactor/Rearchitect

Migration Assessment Framework

Data Migration Strategies

VSAM to Relational Database Migration

Copybook to Schema Converter

Refactoring COBOL Code

Modularization Techniques

Before: Monolithic Structure

After: Modular Structure

Automated Refactoring Tools

COBOL Refactoring Engine

Integration with Modern Languages

COBOL-Java Integration

COBOL Service

Java Integration Layer

COBOL-Python Integration

Python API Gateway for COBOL Services

Cloud Deployment Strategies

Containerization Approach

Dockerfile for COBOL Applications

Kubernetes Deployment

Serverless COBOL Functions

AWS Lambda COBOL Function

Modernization Tools and Techniques

Code Analysis and Discovery Tools

Static Analysis Tools

Runtime Analysis Tools

Custom Modernization Toolkit

COBOL Modernization Assessment Tool

💡 Knowledge Check Quiz

🔧 Practical Exercise

Exercise: Migration Assessment

📚 Related Concepts

Technical Concepts

Business Concepts

🔗 Related Tutorial Pages

Foundation Topics

Advanced Topics

❓ Frequently Asked Questions

Q: How long does a typical COBOL modernization project take?

Q: What are the biggest risks in COBOL migration projects?

Q: Can COBOL applications run efficiently in the cloud?

Q: What's the difference between MIPS and cloud computing costs?

Q: How do you handle COBOL-specific data types in modern systems?

Q: What tools are available for automated COBOL modernization?

🎯 Key Takeaways