COBOL SAME RECORD AREA - Quick Reference

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* Basic SAME RECORD AREA declaration
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT file1 ASSIGN TO "FILE1.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS file1-status.
    
    SELECT file2 ASSIGN TO "FILE2.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS file2-status
        SAME RECORD AREA AS file1.
 
* Multiple files sharing same area
SELECT file3 ASSIGN TO "FILE3.DAT"
    ORGANIZATION IS SEQUENTIAL
    ACCESS MODE IS SEQUENTIAL
    FILE STATUS IS file3-status
    SAME RECORD AREA AS file1.

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* Data Division with shared record area
DATA DIVISION.
FILE SECTION.
FD  file1.
01  file1-record.
    05  file1-field1 PIC X(10).
    05  file1-field2 PIC 9(5).
 
FD  file2.
01  file2-record.
    05  file2-field1 PIC X(10).
    05  file2-field2 PIC 9(5).
 
* Both files use the same memory area
* Only one file can be accessed at a time

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* Processing multiple files sequentially
PROCEDURE DIVISION.
MAIN-PROCESS.
    * Process first file
    OPEN INPUT file1.
    PERFORM UNTIL end-of-file1
        READ file1
            AT END
                MOVE "Y" TO end-of-file1-flag
            NOT AT END
                PERFORM process-file1-record
        END-READ
    END-PERFORM.
    CLOSE file1.
    
    * Process second file (shares same memory area)
    OPEN INPUT file2.
    PERFORM UNTIL end-of-file2
        READ file2
            AT END
                MOVE "Y" TO end-of-file2-flag
            NOT AT END
                PERFORM process-file2-record
        END-READ
    END-PERFORM.
    CLOSE file2.
    
    STOP RUN.
 
PROCESS-FILE1-RECORD.
    * Process file1 record
    DISPLAY "Processing file1: " file1-field1.
    * Additional processing logic here.
 
PROCESS-FILE2-RECORD.
    * Process file2 record (uses same memory area)
    DISPLAY "Processing file2: " file2-field1.
    * Additional processing logic here.

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* Multi-phase file processing
PROCEDURE DIVISION.
MULTI-PHASE-PROCESS.
    * Phase 1: Read input file
    OPEN INPUT input-file.
    PERFORM read-input-records.
    CLOSE input-file.
    
    * Phase 2: Process temporary file
    OPEN INPUT temp-file.
    PERFORM process-temp-records.
    CLOSE temp-file.
    
    * Phase 3: Write output file
    OPEN OUTPUT output-file.
    PERFORM write-output-records.
    CLOSE output-file.
    
    STOP RUN.
 
READ-INPUT-RECORDS.
    PERFORM UNTIL end-of-input
        READ input-file
            AT END
                MOVE "Y" TO end-of-input-flag
            NOT AT END
                PERFORM process-input-record
        END-READ
    END-PERFORM.
 
PROCESS-TEMP-RECORDS.
    PERFORM UNTIL end-of-temp
        READ temp-file
            AT END
                MOVE "Y" TO end-of-temp-flag
            NOT AT END
                PERFORM process-temp-record
        END-READ
    END-PERFORM.
 
WRITE-OUTPUT-RECORDS.
    PERFORM UNTIL end-of-output
        READ output-file
            AT END
                MOVE "Y" TO end-of-output-flag
            NOT AT END
                PERFORM write-output-record
        END-READ
    END-PERFORM.