Scenario - Let us assume two different employee files contain employee information, and create one merged file containing all employee details from two files.

EMPREC -

----+----1----+----2----+----3----+----4----+--
           05 EMP-NUM         PIC 9(05).
           05 FILLER          PIC X(05).
           05 EMP-NAME        PIC X(10).
           05 EMP-DESG        PIC X(09).
           05 FILLER          PIC X(01).
           05 EMP-SALARY      PIC 9(05).
           05 FILLER          PIC X(12).

Input -

MATEPK.EMPFILE.INPUT1

----+----1----+----2----+----3----+----4----+--
E0001EMPLOYEE1     DIR       LOC1 0000100000   
E0002EMPLOYEE2     MGR  DEPT1LOC1 0000080000   
E0004EMPLOYEE4     TL   DEPT1LOC1 0000050000   
E0006EMPLOYEE6     SE   DEPT1LOC1 0000034000

MATEPK.EMPFILE.INPUT2

----+----1----+----2----+----3----+----4----+--
E0003EMPLOYEE3     MGR  DEPT2LOC2 0000075000   
E0005EMPLOYEE5     SSE  DEPT1LOC1 0000045000   
E0007EMPLOYEE7     SSE  DEPT2LOC2 0000046000  

Code -

----+----1----+----2----+----3----+----4----+----5----+
       IDENTIFICATION DIVISION.
       PROGRAM-ID. MERGEFLS. 
       AUTHOR. MTH.

       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT EMPFILE1 ASSIGN TO INPUT1.  
           SELECT EMPFILE2 ASSIGN TO INPUT2.  
           SELECT EMPFILEO ASSIGN TO OUTPUT1. 
           SELECT WORKFILE ASSIGN TO WORK1.
 
       DATA DIVISION.
       FILE SECTION.
	  * Input File1
       FD EMPFILE1
           RECORD CONTAINS 47 CHARACTERS
           DATA RECORD EMP-REC1
           RECORDING MODE F.
       01 EMP-REC1.
          COPY EMPREC.
	  * Input File2
       FD EMPFILE2
           RECORD CONTAINS 47 CHARACTERS
           DATA RECORD EMP-REC2
           RECORDING MODE F.
       01 EMP-REC2.
          COPY EMPREC.
	  * Output file
       FD EMPFILEO
           RECORD CONTAINS 47 CHARACTERS
           DATA RECORD EMP-RECO 
           RECORDING MODE F.
       01 EMP-RECO.
          COPY EMPREC.
	  * Merge work file
       SD WORKFILE
           RECORD CONTAINS 47 CHARACTERS
           DATA RECORD WORK-REC
           RECORDING MODE F.
       01 WORK-REC.
          05 WORK-EMP-NUM         PIC 9(05).
          05 WORK-REM-REC         PIC X(42).

       PROCEDURE DIVISION.
           MERGE WORKFILE
              ON ASCENDING KEY WORK-EMP-NUM
                 USING EMPFILE1, EMPFILE2
                 GIVING EMPFILEO.
           STOP RUN.

JCL -

//MATEPKRJ JOB MSGLEVEL=(1,1),NOTIFY=&SYSUID
//*
//STEP01  EXEC PGM=MERGEFLS
//STEPLIB  DD  DSN=MATEPK.COBOL.LOADLIB,DISP=SHR
//INPUT1   DD  DSN=MATEPK.EMPFILE.INPUT1,DISP=SHR
//INPUT2   DD  DSN=MATEPK.EMPFILE.INPUT2,DISP=SHR
//OUTPUT1  DD  DSN=MATEPK.EMPFILE.OUTPUT1,
//            DISP=(NEW,CATLG,DELETE),
//            SPACE=(TRK,(3,2),RLSE),
//            UNIT=SYSDA,
//            DCB=(DSORG=PS,RECFM=FB,LRECL=47,BLKSIZE=470)
//WORK1    DD  DSN=&&TEMP,
//            DISP=(NEW,DELETE,DELETE),
//            SPACE=(CYL,(10,5),RLSE),
//            UNIT=SYSDA,
//            DCB=(DSORG=PS,RECFM=FB,LRECL=47,BLKSIZE=470)
//SYSOUT   DD  SYSOUT=*  

Output (MATEPK.EMPFILE.OUTPUT1) -

----+----1----+----2----+----3----+----4----+--
E0001EMPLOYEE1     DIR       LOC1 0000100000   
E0002EMPLOYEE2     MGR  DEPT1LOC1 0000080000   
E0003EMPLOYEE3     MGR  DEPT2LOC2 0000075000   
E0004EMPLOYEE4     TL   DEPT1LOC1 0000050000   
E0005EMPLOYEE5     SSE  DEPT1LOC1 0000045000   
E0006EMPLOYEE6     SE   DEPT1LOC1 0000034000   
E0007EMPLOYEE7     SSE  DEPT2LOC2 0000046000   

Explaining Example -

In the above example:

• MERGE statement merges two sorted input files based on the employee number (1-5 bytes) in both files and writes into the output files.

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