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COBOL Tutorial

COBOL EVERY Clause

The EVERY clause represents a fundamental component of checkpoint and restart operations in COBOL, serving as a mechanism for defining periodic recovery points and restart procedures in batch processing environments. This clause embodies fault-tolerant programming principles by providing systematic checkpoint creation, enabling robust recovery mechanisms, and supporting the development of resilient batch applications that can recover from system failures and resume processing from predetermined restart points.

Basic EVERY Usage

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IDENTIFICATION DIVISION.
PROGRAM-ID. EVERY-DEMO.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INPUT-FILE ASSIGN TO 'INPUT.DAT'
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS INPUT-FILE-STATUS.
    
    SELECT OUTPUT-FILE ASSIGN TO 'OUTPUT.DAT'
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS OUTPUT-FILE-STATUS.
    
    SELECT CHECKPOINT-FILE ASSIGN TO 'CHKPT.DAT'
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS CHECKPOINT-FILE-STATUS.
 
I-O-CONTROL.
    RERUN ON CHECKPOINT-FILE EVERY 1000 RECORDS OF INPUT-FILE.
 
DATA DIVISION.
FILE SECTION.
FD  INPUT-FILE.
01  INPUT-RECORD                PIC X(100).
 
FD  OUTPUT-FILE.
01  OUTPUT-RECORD               PIC X(100).
 
FD  CHECKPOINT-FILE.
01  CHECKPOINT-RECORD.
    05  CHECKPOINT-TIMESTAMP    PIC X(14).
    05  RECORDS-PROCESSED       PIC 9(9).
    05  CHECKPOINT-STATUS       PIC X(10).
 
WORKING-STORAGE SECTION.
01  FILE-STATUS-AREAS.
    05  INPUT-FILE-STATUS       PIC XX.
    05  OUTPUT-FILE-STATUS      PIC XX.
    05  CHECKPOINT-FILE-STATUS  PIC XX.
 
01  PROCESSING-CONTROLS.
    05  RECORD-COUNTER          PIC 9(9) VALUE 0.
    05  CHECKPOINT-COUNTER      PIC 9(5) VALUE 0.
    05  TOTAL-PROCESSED         PIC 9(9) VALUE 0.
    05  CHECKPOINT-INTERVAL     PIC 9(5) VALUE 1000.
 
01  RESTART-CONTROLS.
    05  RESTART-FLAG            PIC X VALUE 'N'.
        88  RESTART-REQUIRED    VALUE 'Y'.
        88  NORMAL-START        VALUE 'N'.
    05  RESTART-POINT           PIC 9(9) VALUE 0.
    05  LAST-CHECKPOINT         PIC 9(9) VALUE 0.
 
PROCEDURE DIVISION.
MAIN-PROCESSING.
    PERFORM INITIALIZE-PROCESSING
    PERFORM CHECK-RESTART-REQUIREMENTS
    PERFORM PROCESS-INPUT-FILE
    PERFORM FINALIZE-PROCESSING
    STOP RUN.
 
INITIALIZE-PROCESSING.
    DISPLAY 'Initializing batch processing with checkpoints...'
    
    OPEN INPUT INPUT-FILE
    OPEN OUTPUT OUTPUT-FILE
    OPEN I-O CHECKPOINT-FILE
    
    MOVE 0 TO RECORD-COUNTER
    MOVE 0 TO CHECKPOINT-COUNTER
    MOVE 0 TO TOTAL-PROCESSED
    
    DISPLAY 'Checkpoint interval: ' CHECKPOINT-INTERVAL ' records'.
 
CHECK-RESTART-REQUIREMENTS.
    DISPLAY 'Checking for restart requirements...'
    
    *> Check if checkpoint file exists and has restart information
    READ CHECKPOINT-FILE
        AT END
            DISPLAY 'No checkpoint found - normal start'
            SET NORMAL-START TO TRUE
        NOT AT END
            DISPLAY 'Checkpoint found - restart available'
            MOVE RECORDS-PROCESSED TO RESTART-POINT
            SET RESTART-REQUIRED TO TRUE
            DISPLAY 'Restart point: ' RESTART-POINT ' records'
    END-READ.
 
PROCESS-INPUT-FILE.
    DISPLAY 'Processing input file...'
    
    IF RESTART-REQUIRED
        PERFORM SKIP-TO-RESTART-POINT
    END-IF
    
    PERFORM READ-INPUT-RECORD
    
    PERFORM UNTIL INPUT-FILE-STATUS NOT = '00'
        PERFORM PROCESS-RECORD
        PERFORM CHECK-CHECKPOINT-INTERVAL
        PERFORM READ-INPUT-RECORD
    END-PERFORM
    
    DISPLAY 'Input file processing completed'
    DISPLAY 'Total records processed: ' TOTAL-PROCESSED.
 
SKIP-TO-RESTART-POINT.
    DISPLAY 'Skipping to restart point...'
    
    PERFORM VARYING RECORD-COUNTER FROM 1 BY 1
            UNTIL RECORD-COUNTER > RESTART-POINT
              OR INPUT-FILE-STATUS NOT = '00'
        
        READ INPUT-FILE
            AT END
                DISPLAY 'Unexpected end of file during restart'
                STOP RUN
        END-READ
        
        IF FUNCTION MOD(RECORD-COUNTER, 10000) = 0
            DISPLAY 'Skipped ' RECORD-COUNTER ' records'
        END-IF
    END-PERFORM
    
    DISPLAY 'Restart position reached: ' RECORD-COUNTER ' records'.
 
READ-INPUT-RECORD.
    READ INPUT-FILE
        AT END
            DISPLAY 'End of input file reached'
        NOT AT END
            ADD 1 TO RECORD-COUNTER
    END-READ.
 
PROCESS-RECORD.
    *> Process the input record
    MOVE INPUT-RECORD TO OUTPUT-RECORD
    
    WRITE OUTPUT-RECORD
    
    ADD 1 TO TOTAL-PROCESSED
    
    IF FUNCTION MOD(TOTAL-PROCESSED, 5000) = 0
        DISPLAY 'Processed ' TOTAL-PROCESSED ' records'
    END-IF.
 
CHECK-CHECKPOINT-INTERVAL.
    *> Check if checkpoint interval has been reached
    IF FUNCTION MOD(RECORD-COUNTER, CHECKPOINT-INTERVAL) = 0
        PERFORM CREATE-CHECKPOINT
    END-IF.
 
CREATE-CHECKPOINT.
    DISPLAY 'Creating checkpoint at record ' RECORD-COUNTER
    
    ADD 1 TO CHECKPOINT-COUNTER
    
    *> Write checkpoint information
    MOVE FUNCTION CURRENT-DATE TO CHECKPOINT-TIMESTAMP
    MOVE RECORD-COUNTER TO RECORDS-PROCESSED
    MOVE 'ACTIVE' TO CHECKPOINT-STATUS
    
    REWRITE CHECKPOINT-RECORD
        INVALID KEY
            DISPLAY 'Error writing checkpoint'
        NOT INVALID KEY
            DISPLAY 'Checkpoint ' CHECKPOINT-COUNTER ' created successfully'
            MOVE RECORD-COUNTER TO LAST-CHECKPOINT
    END-REWRITE.
 
FINALIZE-PROCESSING.
    DISPLAY 'Finalizing processing...'
    
    *> Create final checkpoint
    MOVE FUNCTION CURRENT-DATE TO CHECKPOINT-TIMESTAMP
    MOVE RECORD-COUNTER TO RECORDS-PROCESSED
    MOVE 'COMPLETED' TO CHECKPOINT-STATUS
    
    REWRITE CHECKPOINT-RECORD
    
    CLOSE INPUT-FILE
    CLOSE OUTPUT-FILE
    CLOSE CHECKPOINT-FILE
    
    DISPLAY 'Processing Statistics:'
    DISPLAY 'Total records processed: ' TOTAL-PROCESSED
    DISPLAY 'Checkpoints created: ' CHECKPOINT-COUNTER
    DISPLAY 'Last checkpoint at: ' LAST-CHECKPOINT.

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