MainframeMaster

COBOL Communication Section

The Communication Section in COBOL provides a structured approach to inter-program communication by defining communication areas and message formats. This section allows programs to exchange data, coordinate processing activities, and maintain consistent interfaces between different parts of a system. Understanding the Communication Section is essential for building integrated COBOL applications.

Understanding the Communication Section

The Communication Section is part of the Data Division and defines the structure of data that will be exchanged between programs. It provides a standardized way to pass information, handle responses, and manage communication protocols. This approach ensures consistency and reliability in inter-program communication.

Communication Area Definition

1. Basic Communication Area Structure

A communication area is a data structure that defines the format for data exchange between programs. It typically includes input parameters, output results, status indicators, and error handling information. The structure must be consistent between calling and called programs.

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
       IDENTIFICATION DIVISION.
       PROGRAM-ID. COMMUNICATION-SECTION-EXAMPLE.
       *> This program demonstrates communication section usage
       
       DATA DIVISION.
       COMMUNICATION SECTION.
       *> ================================================================
       *> COMMUNICATION AREA DEFINITION
       *> This area defines the structure for inter-program communication
       *> ================================================================
       COMMUNICATION AREA COMM-AREA.
       01 COMMUNICATION-STRUCTURE.
           05 COMM-HEADER.
               10 COMM-PROGRAM-ID      PIC X(8) VALUE 'COMMAREA'.
               10 COMM-VERSION         PIC X(4) VALUE 'V1.0'.
               10 COMM-FUNCTION-CODE   PIC X(10).
               10 COMM-TIMESTAMP       PIC X(20).
           
           05 COMM-INPUT-DATA.
               10 COMM-CUSTOMER-ID     PIC 9(8).
               10 COMM-ACCOUNT-NUMBER  PIC 9(10).
               10 COMM-TRANSACTION-TYPE PIC X(1).
                   88 COMM-DEPOSIT     VALUE 'D'.
                   88 COMM-WITHDRAWAL  VALUE 'W'.
                   88 COMM-TRANSFER    VALUE 'T'.
               10 COMM-AMOUNT          PIC 9(8)V99.
               10 COMM-DESCRIPTION     PIC X(50).
           
           05 COMM-OUTPUT-DATA.
               10 COMM-NEW-BALANCE     PIC 9(10)V99.
               10 COMM-PROCESSING-FEE  PIC 9(6)V99.
               10 COMM-TRANSACTION-ID  PIC X(16).
           
           05 COMM-STATUS-INFO.
               10 COMM-RETURN-CODE     PIC 9(2).
                   88 COMM-SUCCESS     VALUE 00.
                   88 COMM-WARNING     VALUE 01 THROUGH 09.
                   88 COMM-ERROR       VALUE 10 THROUGH 99.
               10 COMM-STATUS-MESSAGE  PIC X(100).
               10 COMM-ERROR-DETAILS   PIC X(200).
       
       WORKING-STORAGE SECTION.
       *> Local processing variables
       01 LOCAL-PROCESSING-DATA.
           05 PROCESSING-START-TIME    PIC 9(8).
           05 PROCESSING-END-TIME      PIC 9(8).
           05 PROCESSING-DURATION      PIC 9(8).
       
       PROCEDURE DIVISION USING COMMUNICATION-STRUCTURE.
       MAIN-COMMUNICATION-PROCESSING.
           DISPLAY 'Starting Communication Section Processing'
           
       *> Initialize communication area
           PERFORM INITIALIZE-COMMUNICATION-AREA
           
       *> Process the communication request
           PERFORM PROCESS-COMMUNICATION-REQUEST
           
       *> Finalize communication area
           PERFORM FINALIZE-COMMUNICATION-AREA
           
           DISPLAY 'Communication Section Processing Completed'
           GOBACK.
       
       INITIALIZE-COMMUNICATION-AREA.
       *> Set up the communication area for processing
           ACCEPT COMM-TIMESTAMP FROM DATE YYYYMMDD
           ACCEPT COMM-TIMESTAMP(9:8) FROM TIME
           MOVE 0 TO COMM-RETURN-CODE
           MOVE SPACES TO COMM-STATUS-MESSAGE
           MOVE SPACES TO COMM-ERROR-DETAILS
           
           DISPLAY 'Communication area initialized'
           DISPLAY 'Program ID: ' COMM-PROGRAM-ID
           DISPLAY 'Version: ' COMM-VERSION
           DISPLAY 'Function: ' COMM-FUNCTION-CODE.
       
       PROCESS-COMMUNICATION-REQUEST.
       *> Process the communication request based on function code
           EVALUATE COMM-FUNCTION-CODE
               WHEN 'VALIDATE'
                   PERFORM VALIDATE-TRANSACTION-REQUEST
               WHEN 'PROCESS'
                   PERFORM PROCESS-TRANSACTION-REQUEST
               WHEN 'INQUIRY'
                   PERFORM INQUIRY-TRANSACTION-REQUEST
               WHEN OTHER
                   PERFORM HANDLE-INVALID-FUNCTION
           END-EVALUATE.
       
       VALIDATE-TRANSACTION-REQUEST.
       *> Validate the transaction request
           DISPLAY 'Validating transaction request...'
           
           IF COMM-CUSTOMER-ID = 0
               MOVE 10 TO COMM-RETURN-CODE
               MOVE 'Invalid customer ID' TO COMM-STATUS-MESSAGE
           ELSE
               IF COMM-AMOUNT <= 0
                   MOVE 11 TO COMM-RETURN-CODE
                   MOVE 'Invalid transaction amount' TO COMM-STATUS-MESSAGE
               ELSE
                   MOVE 0 TO COMM-RETURN-CODE
                   MOVE 'Transaction validation successful' TO COMM-STATUS-MESSAGE
               END-IF
           END-IF.
       
       PROCESS-TRANSACTION-REQUEST.
       *> Process the transaction request
           DISPLAY 'Processing transaction request...'
           
           ACCEPT PROCESSING-START-TIME FROM TIME
           
           EVALUATE COMM-TRANSACTION-TYPE
               WHEN 'D'
                   PERFORM PROCESS-DEPOSIT-TRANSACTION
               WHEN 'W'
                   PERFORM PROCESS-WITHDRAWAL-TRANSACTION
               WHEN 'T'
                   PERFORM PROCESS-TRANSFER-TRANSACTION
               WHEN OTHER
                   MOVE 12 TO COMM-RETURN-CODE
                   MOVE 'Invalid transaction type' TO COMM-STATUS-MESSAGE
           END-EVALUATE
           
           ACCEPT PROCESSING-END-TIME FROM TIME
           COMPUTE PROCESSING-DURATION = PROCESSING-END-TIME - PROCESSING-START-TIME.
       
       PROCESS-DEPOSIT-TRANSACTION.
       *> Process deposit transaction
           DISPLAY 'Processing deposit transaction'
           ADD COMM-AMOUNT TO COMM-NEW-BALANCE
           MOVE 0.00 TO COMM-PROCESSING-FEE
           MOVE 'DEP' TO COMM-TRANSACTION-ID(1:3)
           MOVE COMM-CUSTOMER-ID TO COMM-TRANSACTION-ID(4:8)
           MOVE 0 TO COMM-RETURN-CODE
           MOVE 'Deposit processed successfully' TO COMM-STATUS-MESSAGE.
       
       PROCESS-WITHDRAWAL-TRANSACTION.
       *> Process withdrawal transaction
           DISPLAY 'Processing withdrawal transaction'
           SUBTRACT COMM-AMOUNT FROM COMM-NEW-BALANCE
           MOVE 2.50 TO COMM-PROCESSING-FEE
           MOVE 'WTH' TO COMM-TRANSACTION-ID(1:3)
           MOVE COMM-CUSTOMER-ID TO COMM-TRANSACTION-ID(4:8)
           MOVE 0 TO COMM-RETURN-CODE
           MOVE 'Withdrawal processed successfully' TO COMM-STATUS-MESSAGE.
       
       PROCESS-TRANSFER-TRANSACTION.
       *> Process transfer transaction
           DISPLAY 'Processing transfer transaction'
           SUBTRACT COMM-AMOUNT FROM COMM-NEW-BALANCE
           MOVE 5.00 TO COMM-PROCESSING-FEE
           MOVE 'TRF' TO COMM-TRANSACTION-ID(1:3)
           MOVE COMM-CUSTOMER-ID TO COMM-TRANSACTION-ID(4:8)
           MOVE 0 TO COMM-RETURN-CODE
           MOVE 'Transfer processed successfully' TO COMM-STATUS-MESSAGE.
       
       INQUIRY-TRANSACTION-REQUEST.
       *> Handle inquiry request
           DISPLAY 'Processing inquiry request...'
           MOVE 0 TO COMM-RETURN-CODE
           MOVE 'Inquiry processed successfully' TO COMM-STATUS-MESSAGE.
       
       HANDLE-INVALID-FUNCTION.
       *> Handle invalid function code
           MOVE 13 TO COMM-RETURN-CODE
           MOVE 'Invalid function code: ' COMM-FUNCTION-CODE TO COMM-STATUS-MESSAGE.
       
       FINALIZE-COMMUNICATION-AREA.
       *> Finalize the communication area with results
           DISPLAY 'Finalizing communication area...'
           DISPLAY 'Return code: ' COMM-RETURN-CODE
           DISPLAY 'Status message: ' COMM-STATUS-MESSAGE
           IF COMM-ERROR
               DISPLAY 'Error details: ' COMM-ERROR-DETAILS
           END-IF.

This example demonstrates a comprehensive communication area structure that includes header information, input data, output data, and status information. The communication area provides a standardized interface for inter-program communication, allowing programs to exchange data reliably and handle errors consistently. The structure includes validation, processing, and error handling capabilities.

2. Advanced Communication Patterns

Advanced communication patterns include request-response models, asynchronous communication, error handling, and status reporting. These patterns provide robust communication mechanisms for complex business applications.

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
       IDENTIFICATION DIVISION.
       PROGRAM-ID. ADVANCED-COMMUNICATION.
       *> This program demonstrates advanced communication patterns
       
       DATA DIVISION.
       COMMUNICATION SECTION.
       *> Advanced communication area with multiple message types
       COMMUNICATION AREA ADV-COMM-AREA.
       01 ADVANCED-COMMUNICATION-STRUCTURE.
           05 COMM-CONTROL-BLOCK.
               10 COMM-MESSAGE-TYPE     PIC X(10).
                   88 COMM-REQUEST      VALUE 'REQUEST'.
                   88 COMM-RESPONSE     VALUE 'RESPONSE'.
                   88 COMM-ERROR        VALUE 'ERROR'.
                   88 COMM-STATUS       VALUE 'STATUS'.
               10 COMM-SEQUENCE-NUMBER  PIC 9(6).
               10 COMM-CORRELATION-ID   PIC X(16).
               10 COMM-PRIORITY         PIC 9(1).
               10 COMM-TIMEOUT-VALUE    PIC 9(4).
           
           05 COMM-REQUEST-DATA.
               10 COMM-OPERATION-CODE   PIC X(4).
               10 COMM-REQUEST-PARAMS.
                   15 COMM-PARAM-COUNT PIC 9(2).
                   15 COMM-PARAMETERS OCCURS 10 TIMES.
                       20 COMM-PARAM-NAME  PIC X(20).
                       20 COMM-PARAM-VALUE PIC X(100).
           
           05 COMM-RESPONSE-DATA.
               10 COMM-RESPONSE-CODE   PIC 9(3).
               10 COMM-RESPONSE-MESSAGE PIC X(200).
               10 COMM-RESULT-DATA.
                   15 COMM-RESULT-COUNT PIC 9(2).
                   15 COMM-RESULTS OCCURS 10 TIMES.
                       20 COMM-RESULT-NAME  PIC X(20).
                       20 COMM-RESULT-VALUE PIC X(100).
           
           05 COMM-ERROR-DATA.
               10 COMM-ERROR-CODE      PIC X(4).
               10 COMM-ERROR-SEVERITY  PIC X(1).
                   88 COMM-CRITICAL     VALUE 'C'.
                   88 COMM-WARNING      VALUE 'W'.
                   88 COMM-INFO         VALUE 'I'.
               10 COMM-ERROR-MESSAGE   PIC X(200).
               10 COMM-ERROR-DETAILS   PIC X(500).
           
           05 COMM-STATUS-DATA.
               10 COMM-PROCESSING-STATUS PIC X(1).
                   88 COMM-ACTIVE       VALUE 'A'.
                   88 COMM-PENDING      VALUE 'P'.
                   88 COMM-COMPLETED    VALUE 'C'.
                   88 COMM-FAILED       VALUE 'F'.
               10 COMM-PROGRESS-PERCENT PIC 9(3).
               10 COMM-ESTIMATED-TIME  PIC 9(4).
       
       WORKING-STORAGE SECTION.
       *> Communication processing variables
       01 COMM-PROCESSING-CONTROLS.
           05 COMM-RETRY-COUNT        PIC 9(2) VALUE 0.
           05 COMM-MAX-RETRIES        PIC 9(2) VALUE 3.
           05 COMM-CURRENT-SEQUENCE   PIC 9(6) VALUE 0.
       
       PROCEDURE DIVISION USING ADVANCED-COMMUNICATION-STRUCTURE.
       MAIN-ADVANCED-COMMUNICATION.
           DISPLAY 'Starting Advanced Communication Processing'
           
       *> Initialize advanced communication
           PERFORM INITIALIZE-ADVANCED-COMMUNICATION
           
       *> Process based on message type
           PERFORM PROCESS-MESSAGE-TYPE
           
       *> Finalize communication
           PERFORM FINALIZE-ADVANCED-COMMUNICATION
           
           DISPLAY 'Advanced Communication Processing Completed'
           GOBACK.
       
       INITIALIZE-ADVANCED-COMMUNICATION.
       *> Set up advanced communication processing
           ADD 1 TO COMM-CURRENT-SEQUENCE
           MOVE COMM-CURRENT-SEQUENCE TO COMM-SEQUENCE-NUMBER
           MOVE 1 TO COMM-PRIORITY
           MOVE 30 TO COMM-TIMEOUT-VALUE
           
           DISPLAY 'Advanced communication initialized'
           DISPLAY 'Sequence number: ' COMM-SEQUENCE-NUMBER
           DISPLAY 'Message type: ' COMM-MESSAGE-TYPE.
       
       PROCESS-MESSAGE-TYPE.
       *> Process communication based on message type
           EVALUATE TRUE
               WHEN COMM-REQUEST
                   PERFORM PROCESS-REQUEST-MESSAGE
               WHEN COMM-RESPONSE
                   PERFORM PROCESS-RESPONSE-MESSAGE
               WHEN COMM-ERROR
                   PERFORM PROCESS-ERROR-MESSAGE
               WHEN COMM-STATUS
                   PERFORM PROCESS-STATUS-MESSAGE
               WHEN OTHER
                   PERFORM HANDLE-UNKNOWN-MESSAGE-TYPE
           END-EVALUATE.
       
       PROCESS-REQUEST-MESSAGE.
       *> Process request message
           DISPLAY 'Processing request message...'
           
           EVALUATE COMM-OPERATION-CODE
               WHEN 'VALD'
                   PERFORM VALIDATE-REQUEST-PARAMETERS
               WHEN 'PROC'
                   PERFORM PROCESS-REQUEST-PARAMETERS
               WHEN 'INQR'
                   PERFORM INQUIRY-REQUEST-PARAMETERS
               WHEN OTHER
                   PERFORM HANDLE-INVALID-OPERATION
           END-EVALUATE.
       
       VALIDATE-REQUEST-PARAMETERS.
       *> Validate request parameters
           DISPLAY 'Validating request parameters...'
           
           IF COMM-PARAM-COUNT = 0
               MOVE 'VALD' TO COMM-ERROR-CODE
               SET COMM-CRITICAL TO TRUE
               MOVE 'No parameters provided for validation' TO COMM-ERROR-MESSAGE
           ELSE
               MOVE 0 TO COMM-RESPONSE-CODE
               MOVE 'Parameters validated successfully' TO COMM-RESPONSE-MESSAGE
           END-IF.
       
       PROCESS-REQUEST-PARAMETERS.
       *> Process request parameters
           DISPLAY 'Processing request parameters...'
           
           MOVE 0 TO COMM-RESPONSE-CODE
           MOVE 'Parameters processed successfully' TO COMM-RESPONSE-MESSAGE
           MOVE COMM-PARAM-COUNT TO COMM-RESULT-COUNT.
       
       INQUIRY-REQUEST-PARAMETERS.
       *> Handle inquiry request
           DISPLAY 'Processing inquiry request...'
           
           MOVE 0 TO COMM-RESPONSE-CODE
           MOVE 'Inquiry completed successfully' TO COMM-RESPONSE-MESSAGE.
       
       HANDLE-INVALID-OPERATION.
       *> Handle invalid operation code
           MOVE 'INOP' TO COMM-ERROR-CODE
           SET COMM-WARNING TO TRUE
           MOVE 'Invalid operation code: ' COMM-OPERATION-CODE TO COMM-ERROR-MESSAGE.
       
       PROCESS-RESPONSE-MESSAGE.
       *> Process response message
           DISPLAY 'Processing response message...'
           DISPLAY 'Response code: ' COMM-RESPONSE-CODE
           DISPLAY 'Response message: ' COMM-RESPONSE-MESSAGE.
       
       PROCESS-ERROR-MESSAGE.
       *> Process error message
           DISPLAY 'Processing error message...'
           DISPLAY 'Error code: ' COMM-ERROR-CODE
           DISPLAY 'Error severity: ' COMM-ERROR-SEVERITY
           DISPLAY 'Error message: ' COMM-ERROR-MESSAGE
           
           IF COMM-CRITICAL
               DISPLAY 'CRITICAL ERROR: Immediate attention required'
           ELSE
               IF COMM-WARNING
                   DISPLAY 'WARNING: Error logged but processing continues'
               ELSE
                   DISPLAY 'INFO: Error logged for monitoring'
               END-IF
           END-IF.
       
       PROCESS-STATUS-MESSAGE.
       *> Process status message
           DISPLAY 'Processing status message...'
           DISPLAY 'Processing status: ' COMM-PROCESSING-STATUS
           DISPLAY 'Progress: ' COMM-PROGRESS-PERCENT '%'
           DISPLAY 'Estimated time: ' COMM-ESTIMATED-TIME ' seconds'.
       
       HANDLE-UNKNOWN-MESSAGE-TYPE.
       *> Handle unknown message type
           MOVE 'UNKN' TO COMM-ERROR-CODE
           SET COMM-WARNING TO TRUE
           MOVE 'Unknown message type: ' COMM-MESSAGE-TYPE TO COMM-ERROR-MESSAGE.
       
       FINALIZE-ADVANCED-COMMUNICATION.
       *> Finalize advanced communication processing
           DISPLAY 'Finalizing advanced communication...'
           DISPLAY 'Communication processing completed successfully'.

This advanced example demonstrates sophisticated communication patterns including message types, sequence numbers, correlation IDs, priority handling, and comprehensive error management. The communication structure supports multiple message types (request, response, error, status) and provides robust error handling with different severity levels. This approach enables complex inter-program communication scenarios.

Communication Section Best Practices

Common Communication Patterns

Communication Handling

Learn communication handling techniques

Call Statement

Master CALL statement techniques

Program Communication

Learn program communication

Data Exchange

Learn data exchange techniques

Message Handling

Master message handling

Error Handling

Master error handling