MainframeMaster

COBOL Tutorial

COBOL CHAIN and CHAINING

The CHAIN and CHAINING statements in COBOL provide powerful program control transfer mechanisms that enable one program to transfer control to another program while preserving data and execution context. These statements are essential for modular programming, system integration, workflow management, and building complex application architectures where programs need to pass control and data between different modules in a structured and efficient manner while maintaining program state and parameter continuity across program boundaries.

Understanding CHAIN and CHAINING

CHAIN transfers control from the current program to another program, effectively replacing the current program in memory. CHAINING refers to the overall concept of linking programs together in a sequence. Unlike CALL, CHAIN does not return control to the calling program.

Key Features:

  • Program-to-program control transfer
  • Parameter and data passing
  • Memory management and optimization
  • Workflow and process control
  • Modular application architecture
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
*> Basic CHAIN statement usage
DATA DIVISION.
WORKING-STORAGE SECTION.
01  CHAIN-PARAMETERS.
    05  NEXT-PROGRAM       PIC X(8) VALUE "PROG002".
    05  CHAIN-DATA         PIC X(100).
    05  PROCESS-STATUS     PIC X VALUE 'A'.
        88  CONTINUE-PROCESSING VALUE 'A'.
        88  END-PROCESSING     VALUE 'Z'.
 
01  PROGRAM-CONTROL.
    05  CURRENT-STEP       PIC 9(2) VALUE 1.
    05  TOTAL-STEPS        PIC 9(2) VALUE 5.
    05  ERROR-FLAG         PIC X VALUE 'N'.
        88  ERROR-OCCURRED VALUE 'Y'.
 
PROCEDURE DIVISION.
MAIN-PROGRAM-LOGIC.
    PERFORM INITIALIZE-PROCESSING
    PERFORM PROCESS-CURRENT-STEP
    
    IF CONTINUE-PROCESSING AND NOT ERROR-OCCURRED
        PERFORM PREPARE-CHAIN-DATA
        PERFORM CHAIN-TO-NEXT-PROGRAM
    ELSE
        PERFORM END-PROGRAM-PROCESSING
    END-IF.
 
PROCESS-CURRENT-STEP.
    DISPLAY "Processing step: " CURRENT-STEP
    
    EVALUATE CURRENT-STEP
        WHEN 1
            PERFORM VALIDATE-INPUT-DATA
        WHEN 2
            PERFORM CALCULATE-RESULTS
        WHEN 3
            PERFORM UPDATE-DATABASE
        WHEN OTHER
            PERFORM FINALIZE-PROCESSING
    END-EVALUATE.
 
PREPARE-CHAIN-DATA.
    STRING "STEP=" CURRENT-STEP 
           ",STATUS=" PROCESS-STATUS
           ",DATA=" WS-CALCULATED-VALUE
        DELIMITED BY SIZE INTO CHAIN-DATA
    END-STRING.
 
CHAIN-TO-NEXT-PROGRAM.
    DISPLAY "Chaining to program: " NEXT-PROGRAM
    CHAIN NEXT-PROGRAM USING CHAIN-DATA.

Advanced Program Chaining

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
*> Advanced program chaining with complex data structures
DATA DIVISION.
WORKING-STORAGE SECTION.
01  CHAINING-CONTROL-BLOCK.
    05  CCB-SIGNATURE      PIC X(4) VALUE "CCB1".
    05  CCB-VERSION        PIC 9(2) VALUE 01.
    05  CCB-PROGRAM-COUNT  PIC 9(3) VALUE ZERO.
    05  CCB-CURRENT-PROG   PIC 9(3) VALUE 1.
    05  CCB-STATUS         PIC X(2) VALUE "OK".
    05  CCB-ERROR-CODE     PIC 9(4) VALUE ZERO.
 
01  PROGRAM-CHAIN-TABLE.
    05  CHAIN-PROGRAMS     OCCURS 10 TIMES.
        10  PROG-NAME      PIC X(8).
        10  PROG-FUNCTION  PIC X(20).
        10  PROG-STATUS    PIC X(1).
            88  PROG-PENDING    VALUE 'P'.
            88  PROG-RUNNING    VALUE 'R'.
            88  PROG-COMPLETED  VALUE 'C'.
            88  PROG-ERROR      VALUE 'E'.
        10  PROG-PRIORITY  PIC 9(2).
 
01  SHARED-DATA-AREA.
    05  SDA-CUSTOMER-DATA.
        10  CUSTOMER-ID    PIC 9(8).
        10  CUSTOMER-NAME  PIC X(30).
        10  CUSTOMER-TYPE  PIC X(3).
    05  SDA-TRANSACTION-DATA.
        10  TRANS-COUNT    PIC 9(5).
        10  TRANS-AMOUNT   PIC S9(9)V99 COMP-3.
        10  TRANS-DATE     PIC 9(8).
    05  SDA-CONTROL-INFO.
        10  PROCESSING-MODE PIC X(10).
        10  BATCH-NUMBER   PIC 9(6).
        10  RUN-DATE       PIC 9(8).
 
PROCEDURE DIVISION.
ADVANCED-CHAINING-CONTROL.
    PERFORM INITIALIZE-CHAIN-TABLE
    PERFORM SETUP-SHARED-DATA
    PERFORM EXECUTE-PROGRAM-CHAIN.
 
INITIALIZE-CHAIN-TABLE.
    *> Set up the program execution sequence
    MOVE "VALIDATE" TO PROG-NAME(1)
    MOVE "Input Validation" TO PROG-FUNCTION(1)
    MOVE 'P' TO PROG-STATUS(1)
    MOVE 10 TO PROG-PRIORITY(1)
    
    MOVE "PROCESS1" TO PROG-NAME(2)
    MOVE "Data Processing" TO PROG-FUNCTION(2)
    MOVE 'P' TO PROG-STATUS(2)
    MOVE 20 TO PROG-PRIORITY(2)
    
    MOVE "PROCESS2" TO PROG-NAME(3)
    MOVE "Business Logic" TO PROG-FUNCTION(3)
    MOVE 'P' TO PROG-STATUS(3)
    MOVE 30 TO PROG-PRIORITY(3)
    
    MOVE "REPORT" TO PROG-NAME(4)
    MOVE "Report Generation" TO PROG-FUNCTION(4)
    MOVE 'P' TO PROG-STATUS(4)
    MOVE 40 TO PROG-PRIORITY(4)
    
    MOVE 4 TO CCB-PROGRAM-COUNT.
 
SETUP-SHARED-DATA.
    *> Initialize shared data for the chain
    MOVE 12345678 TO CUSTOMER-ID
    MOVE "ACME CORPORATION" TO CUSTOMER-NAME
    MOVE "BUS" TO CUSTOMER-TYPE
    
    MOVE 150 TO TRANS-COUNT
    MOVE 250000.00 TO TRANS-AMOUNT
    MOVE FUNCTION CURRENT-DATE(1:8) TO TRANS-DATE
    
    MOVE "BATCH" TO PROCESSING-MODE
    MOVE 123456 TO BATCH-NUMBER
    MOVE FUNCTION CURRENT-DATE(1:8) TO RUN-DATE.
 
EXECUTE-PROGRAM-CHAIN.
    PERFORM VARYING CCB-CURRENT-PROG FROM 1 BY 1
        UNTIL CCB-CURRENT-PROG > CCB-PROGRAM-COUNT
           OR CCB-STATUS NOT = "OK"
        
        PERFORM PREPARE-PROGRAM-EXECUTION
        PERFORM CHAIN-TO-CURRENT-PROGRAM
    END-PERFORM.
 
PREPARE-PROGRAM-EXECUTION.
    MOVE 'R' TO PROG-STATUS(CCB-CURRENT-PROG)
    
    DISPLAY "Executing program: " 
            PROG-NAME(CCB-CURRENT-PROG)
    DISPLAY "Function: " 
            PROG-FUNCTION(CCB-CURRENT-PROG)
    DISPLAY "Priority: " 
            PROG-PRIORITY(CCB-CURRENT-PROG).
 
CHAIN-TO-CURRENT-PROGRAM.
    *> Pass control and data to the next program
    EVALUATE CCB-CURRENT-PROG
        WHEN 1
            CHAIN "VALIDATE" USING 
                CHAINING-CONTROL-BLOCK
                SHARED-DATA-AREA
        WHEN 2
            CHAIN "PROCESS1" USING 
                CHAINING-CONTROL-BLOCK
                SHARED-DATA-AREA
        WHEN 3
            CHAIN "PROCESS2" USING 
                CHAINING-CONTROL-BLOCK
                SHARED-DATA-AREA
        WHEN 4
            CHAIN "REPORT" USING 
                CHAINING-CONTROL-BLOCK
                SHARED-DATA-AREA
        WHEN OTHER
            MOVE "ER" TO CCB-STATUS
            MOVE 9999 TO CCB-ERROR-CODE
    END-EVALUATE.

Workflow Management System

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
*> Workflow management using program chaining
DATA DIVISION.
WORKING-STORAGE SECTION.
01  WORKFLOW-CONTROL.
    05  WF-ID              PIC 9(8).
    05  WF-NAME            PIC X(30).
    05  WF-STATUS          PIC X(10).
        88  WF-ACTIVE      VALUE "ACTIVE".
        88  WF-SUSPENDED   VALUE "SUSPENDED".
        88  WF-COMPLETED   VALUE "COMPLETED".
        88  WF-ERROR       VALUE "ERROR".
    05  WF-CURRENT-STEP    PIC 9(3).
    05  WF-TOTAL-STEPS     PIC 9(3).
    05  WF-START-TIME      PIC X(26).
    05  WF-END-TIME        PIC X(26).
 
01  WORKFLOW-STEPS.
    05  STEP-DEFINITIONS   OCCURS 50 TIMES.
        10  STEP-NUMBER    PIC 9(3).
        10  STEP-NAME      PIC X(20).
        10  STEP-PROGRAM   PIC X(8).
        10  STEP-TYPE      PIC X(10).
            88  STEP-PROCESS   VALUE "PROCESS".
            88  STEP-DECISION  VALUE "DECISION".
            88  STEP-MANUAL    VALUE "MANUAL".
            88  STEP-AUTOMATED VALUE "AUTOMATED".
        10  STEP-STATUS    PIC X(10).
        10  STEP-DURATION  PIC 9(5).
        10  STEP-RETRY-COUNT PIC 9(2).
 
01  BUSINESS-PROCESS-DATA.
    05  ORDER-INFORMATION.
        10  ORDER-ID       PIC 9(10).
        10  ORDER-DATE     PIC 9(8).
        10  ORDER-VALUE    PIC S9(9)V99 COMP-3.
        10  ORDER-STATUS   PIC X(10).
    05  APPROVAL-CHAIN.
        10  APPROVAL-LEVEL PIC 9(2).
        10  APPROVER-ID    PIC X(8).
        10  APPROVAL-DATE  PIC 9(8).
        10  APPROVAL-STATUS PIC X(10).
 
PROCEDURE DIVISION.
WORKFLOW-MANAGEMENT-SYSTEM.
    PERFORM INITIALIZE-WORKFLOW
    PERFORM DEFINE-WORKFLOW-STEPS
    PERFORM EXECUTE-WORKFLOW-CHAIN.
 
INITIALIZE-WORKFLOW.
    MOVE 20231001 TO WF-ID
    MOVE "ORDER-PROCESSING-WORKFLOW" TO WF-NAME
    MOVE "ACTIVE" TO WF-STATUS
    MOVE 1 TO WF-CURRENT-STEP
    MOVE 8 TO WF-TOTAL-STEPS
    MOVE FUNCTION CURRENT-DATE TO WF-START-TIME.
 
DEFINE-WORKFLOW-STEPS.
    *> Step 1: Order Validation
    MOVE 1 TO STEP-NUMBER(1)
    MOVE "Order Validation" TO STEP-NAME(1)
    MOVE "ORDVAL" TO STEP-PROGRAM(1)
    MOVE "AUTOMATED" TO STEP-TYPE(1)
    MOVE "PENDING" TO STEP-STATUS(1)
    
    *> Step 2: Credit Check
    MOVE 2 TO STEP-NUMBER(2)
    MOVE "Credit Check" TO STEP-NAME(2)
    MOVE "CREDCHK" TO STEP-PROGRAM(2)
    MOVE "AUTOMATED" TO STEP-TYPE(2)
    MOVE "PENDING" TO STEP-STATUS(2)
    
    *> Step 3: Inventory Check
    MOVE 3 TO STEP-NUMBER(3)
    MOVE "Inventory Check" TO STEP-NAME(3)
    MOVE "INVCHK" TO STEP-PROGRAM(3)
    MOVE "AUTOMATED" TO STEP-TYPE(3)
    MOVE "PENDING" TO STEP-STATUS(3)
    
    *> Step 4: Approval Process
    MOVE 4 TO STEP-NUMBER(4)
    MOVE "Approval Process" TO STEP-NAME(4)
    MOVE "APPROVE" TO STEP-PROGRAM(4)
    MOVE "DECISION" TO STEP-TYPE(4)
    MOVE "PENDING" TO STEP-STATUS(4)
    
    *> Step 5: Order Fulfillment
    MOVE 5 TO STEP-NUMBER(5)
    MOVE "Order Fulfillment" TO STEP-NAME(5)
    MOVE "FULFILL" TO STEP-PROGRAM(5)
    MOVE "PROCESS" TO STEP-TYPE(5)
    MOVE "PENDING" TO STEP-STATUS(5)
    
    *> Step 6: Shipping
    MOVE 6 TO STEP-NUMBER(6)
    MOVE "Shipping Process" TO STEP-NAME(6)
    MOVE "SHIP" TO STEP-PROGRAM(6)
    MOVE "PROCESS" TO STEP-TYPE(6)
    MOVE "PENDING" TO STEP-STATUS(6)
    
    *> Step 7: Invoice Generation
    MOVE 7 TO STEP-NUMBER(7)
    MOVE "Invoice Generation" TO STEP-NAME(7)
    MOVE "INVOICE" TO STEP-PROGRAM(7)
    MOVE "AUTOMATED" TO STEP-TYPE(7)
    MOVE "PENDING" TO STEP-STATUS(7)
    
    *> Step 8: Completion
    MOVE 8 TO STEP-NUMBER(8)
    MOVE "Order Completion" TO STEP-NAME(8)
    MOVE "COMPLETE" TO STEP-PROGRAM(8)
    MOVE "AUTOMATED" TO STEP-TYPE(8)
    MOVE "PENDING" TO STEP-STATUS(8).
 
EXECUTE-WORKFLOW-CHAIN.
    PERFORM VARYING WF-CURRENT-STEP FROM 1 BY 1
        UNTIL WF-CURRENT-STEP > WF-TOTAL-STEPS
           OR WF-ERROR
        
        PERFORM LOG-WORKFLOW-STEP
        PERFORM EXECUTE-CURRENT-STEP
        PERFORM UPDATE-STEP-STATUS
        
        IF WF-ERROR
            PERFORM HANDLE-WORKFLOW-ERROR
            EXIT PERFORM
        END-IF
    END-PERFORM
    
    IF NOT WF-ERROR
        PERFORM COMPLETE-WORKFLOW
    END-IF.
 
EXECUTE-CURRENT-STEP.
    MOVE "RUNNING" TO STEP-STATUS(WF-CURRENT-STEP)
    
    DISPLAY "Executing workflow step: " WF-CURRENT-STEP
    DISPLAY "Step name: " STEP-NAME(WF-CURRENT-STEP)
    DISPLAY "Program: " STEP-PROGRAM(WF-CURRENT-STEP)
    
    *> Chain to the appropriate program for this step
    EVALUATE WF-CURRENT-STEP
        WHEN 1 THRU 8
            CHAIN STEP-PROGRAM(WF-CURRENT-STEP) USING 
                WORKFLOW-CONTROL
                WORKFLOW-STEPS
                BUSINESS-PROCESS-DATA
        WHEN OTHER
            MOVE "ERROR" TO WF-STATUS
    END-EVALUATE.
 
LOG-WORKFLOW-STEP.
    DISPLAY "=== Workflow Step Execution ==="
    DISPLAY "Workflow ID: " WF-ID
    DISPLAY "Workflow Name: " WF-NAME
    DISPLAY "Current Step: " WF-CURRENT-STEP " of " WF-TOTAL-STEPS
    DISPLAY "Step Name: " STEP-NAME(WF-CURRENT-STEP)
    DISPLAY "Step Type: " STEP-TYPE(WF-CURRENT-STEP).
 
UPDATE-STEP-STATUS.
    MOVE "COMPLETED" TO STEP-STATUS(WF-CURRENT-STEP)
    ADD 1 TO WF-CURRENT-STEP.
 
COMPLETE-WORKFLOW.
    MOVE "COMPLETED" TO WF-STATUS
    MOVE FUNCTION CURRENT-DATE TO WF-END-TIME
    
    DISPLAY "=== Workflow Completed ==="
    DISPLAY "Workflow ID: " WF-ID
    DISPLAY "Start Time: " WF-START-TIME
    DISPLAY "End Time: " WF-END-TIME.

Error Handling and Recovery

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
*> Error handling and recovery in program chains
DATA DIVISION.
WORKING-STORAGE SECTION.
01  ERROR-RECOVERY-CONTROL.
    05  ERROR-HANDLER-PROG PIC X(8) VALUE "ERRHAND".
    05  RECOVERY-PROG      PIC X(8) VALUE "RECOVERY".
    05  ROLLBACK-PROG      PIC X(8) VALUE "ROLLBACK".
    05  AUDIT-PROG         PIC X(8) VALUE "AUDIT".
 
01  ERROR-INFORMATION.
    05  ERROR-CODE         PIC 9(4).
    05  ERROR-MESSAGE      PIC X(80).
    05  ERROR-SEVERITY     PIC X(10).
        88  FATAL-ERROR    VALUE "FATAL".
        88  WARNING-ERROR  VALUE "WARNING".
        88  INFO-ERROR     VALUE "INFO".
    05  ERROR-PROGRAM      PIC X(8).
    05  ERROR-TIMESTAMP    PIC X(26).
    05  ERROR-USER-ID      PIC X(8).
 
01  RECOVERY-OPTIONS.
    05  RECOVERY-ACTION    PIC X(10).
        88  RETRY-OPERATION   VALUE "RETRY".
        88  SKIP-STEP        VALUE "SKIP".
        88  ABORT-CHAIN      VALUE "ABORT".
        88  MANUAL-INTERVENTION VALUE "MANUAL".
    05  RETRY-COUNT        PIC 9(2) VALUE ZERO.
    05  MAX-RETRIES        PIC 9(2) VALUE 3.
 
01  CHECKPOINT-DATA.
    05  CHECKPOINT-ID      PIC 9(8).
    05  CHECKPOINT-STATUS  PIC X(10).
    05  CHECKPOINT-DATA-AREA PIC X(500).
 
PROCEDURE DIVISION.
ERROR-HANDLING-CHAIN.
    PERFORM INITIALIZE-ERROR-HANDLING
    PERFORM MAIN-PROCESSING-WITH-RECOVERY.
 
INITIALIZE-ERROR-HANDLING.
    MOVE FUNCTION CURRENT-DATE TO ERROR-TIMESTAMP
    MOVE "SYSTEM" TO ERROR-USER-ID
    MOVE ZERO TO ERROR-CODE RETRY-COUNT.
 
MAIN-PROCESSING-WITH-RECOVERY.
    PERFORM ESTABLISH-CHECKPOINT
    
    PERFORM UNTIL OPERATION-COMPLETE OR ABORT-CHAIN
        PERFORM ATTEMPT-OPERATION
        
        IF ERROR-OCCURRED
            PERFORM HANDLE-CHAIN-ERROR
            
            EVALUATE TRUE
                WHEN RETRY-OPERATION
                    PERFORM INCREMENT-RETRY-COUNT
                    IF RETRY-COUNT <= MAX-RETRIES
                        CONTINUE
                    ELSE
                        PERFORM ESCALATE-ERROR
                    END-IF
                WHEN SKIP-STEP
                    PERFORM SKIP-TO-NEXT-STEP
                WHEN ABORT-CHAIN
                    PERFORM ABORT-PROCESSING-CHAIN
                WHEN MANUAL-INTERVENTION
                    PERFORM REQUEST-MANUAL-INTERVENTION
            END-EVALUATE
        ELSE
            PERFORM ADVANCE-TO-NEXT-STEP
        END-IF
    END-PERFORM.
 
ATTEMPT-OPERATION.
    *> Simulate processing that might fail
    EVALUATE WS-CURRENT-OPERATION
        WHEN "DATABASE-UPDATE"
            PERFORM UPDATE-DATABASE-OPERATION
        WHEN "FILE-PROCESSING"
            PERFORM FILE-PROCESSING-OPERATION
        WHEN "CALCULATION"
            PERFORM CALCULATION-OPERATION
        WHEN OTHER
            PERFORM UNKNOWN-OPERATION
    END-EVALUATE.
 
HANDLE-CHAIN-ERROR.
    MOVE "ERROR" TO ERROR-SEVERITY
    MOVE WS-CURRENT-PROGRAM TO ERROR-PROGRAM
    MOVE FUNCTION CURRENT-DATE TO ERROR-TIMESTAMP
    
    DISPLAY "=== Error Detected in Chain ==="
    DISPLAY "Error Code: " ERROR-CODE
    DISPLAY "Error Message: " ERROR-MESSAGE
    DISPLAY "Program: " ERROR-PROGRAM
    DISPLAY "Timestamp: " ERROR-TIMESTAMP
    
    *> Chain to error handler program
    CHAIN ERROR-HANDLER-PROG USING 
        ERROR-INFORMATION
        RECOVERY-OPTIONS
        CHECKPOINT-DATA.
 
ESTABLISH-CHECKPOINT.
    MOVE FUNCTION CURRENT-DATE(9:8) TO CHECKPOINT-ID
    MOVE "ACTIVE" TO CHECKPOINT-STATUS
    
    *> Save current state
    STRING "PROGRAM=" WS-CURRENT-PROGRAM
           ",STEP=" WS-CURRENT-STEP
           ",STATUS=" WS-PROCESS-STATUS
        DELIMITED BY SIZE INTO CHECKPOINT-DATA-AREA
    END-STRING
    
    DISPLAY "Checkpoint established: " CHECKPOINT-ID.
 
ESCALATE-ERROR.
    MOVE "FATAL" TO ERROR-SEVERITY
    MOVE "Maximum retries exceeded" TO ERROR-MESSAGE
    
    *> Chain to escalation handler
    CHAIN "ESCALATE" USING 
        ERROR-INFORMATION
        CHECKPOINT-DATA.
 
SKIP-TO-NEXT-STEP.
    DISPLAY "Skipping current step due to error"
    ADD 1 TO WS-CURRENT-STEP
    MOVE ZERO TO RETRY-COUNT.
 
ABORT-PROCESSING-CHAIN.
    MOVE "FATAL" TO ERROR-SEVERITY
    MOVE "Processing chain aborted" TO ERROR-MESSAGE
    
    *> Chain to rollback program
    CHAIN ROLLBACK-PROG USING 
        ERROR-INFORMATION
        CHECKPOINT-DATA.
 
REQUEST-MANUAL-INTERVENTION.
    MOVE "WARNING" TO ERROR-SEVERITY
    MOVE "Manual intervention required" TO ERROR-MESSAGE
    
    DISPLAY "=== Manual Intervention Required ==="
    DISPLAY "Current Step: " WS-CURRENT-STEP
    DISPLAY "Error: " ERROR-MESSAGE
    DISPLAY "Please resolve and restart"
    
    *> Chain to manual intervention handler
    CHAIN "MANUAL" USING 
        ERROR-INFORMATION
        RECOVERY-OPTIONS
        CHECKPOINT-DATA.

Best Practices

CHAIN and CHAINING Guidelines:

  • Design clear program interfaces and parameter structures
  • Implement robust error handling and recovery mechanisms
  • Use consistent naming conventions for chained programs
  • Document program dependencies and execution flows
  • Implement checkpoint and restart capabilities
  • Consider memory usage and resource management
  • Test chain sequences thoroughly with various scenarios

FAQ

Q: How does CHAIN differ from CALL?

CHAIN transfers control permanently to another program and doesn't return, while CALL temporarily transfers control and returns to the calling program.

Q: Can I pass data between chained programs?

Yes, you can pass data using the USING clause in the CHAIN statement, similar to how parameters are passed in CALL statements.

Q: What happens to memory when chaining?

The current program is typically removed from memory and replaced by the chained program, making CHAIN memory-efficient for long processing sequences.