IBM Mainframe Tutorial

In JCL , we can concatenate different files by giving their name one after
   another. All data sets concated must be of the same type. For example,
   partitioned data sets can be concatenated only with partitioned data sets.

      Example JCL  -->   //MYJOB   JOB   (W345),'KRISHNA REDDY'
                         //STEP1   EXEC  PGM=COBPROG
                         //INFILE  DD    DSN=TEST.GLOB.FILE1
                         //              DSN=TEST.GLOB.FILE2
                         //              DSN=TEST.GLOB.FILE3

      In program , we will read it as an single file. concatination of three
      files done by operating system.