In this example, you can label a tape in one step of a job, and then, without the system demounting and remounting that tape between steps, write to the tape in a subsequent step of the same job. The necessary JCL code follows:

           //STEP1     EXEC PGM=IEHINITT
           //SYSPRINT  DD  SYSOUT=*
      (1)  //LABEL     DD  UNIT=(tape,1,DEFER),DISP=(,PASS)
           //SYSIN     DD    *
      (2)  LABEL   INITT  SER=serial,DISP=REWIND
           //*
           //STEP2   EXEC PGM=user_program
           //INPUT   DD  DSN=input_dsn,DISP=SHR
           //OUTPUT  DD  DSN=dsname,DISP=(NEW,CATLG),
           //             DCB=(dcbinfo),
      (3)  //             UNIT=tape,VOL=(,RETAIN,SER=serial)
      Notes:
           (1) Either DISP=(NEW,PASS) or VOL=(,RETAIN) must be specified.
           (2) DISP=REWIND must be specified on the INITT statement.
           (3) VOL=SER=serial must be specified.
               VOL=REF=*.STEP1.LABEL will not work.