In this example, a blocked copy on tape is made from an unblocked sequential disk file. Because the disk data set has a relatively small block size, the number of buffers explicitly requested is larger than the default of five. This improves performance by permitting more overlap of reading the SYSUT1 data set with writing the SYSUT2 data set.

  //COPYJOB  JOB
  //STEP1    EXEC PGM=IEBGENER,REGION=318K
  //SYSPRINT DD  SYSOUT=A
  //SYSIN    DD  DUMMY
  //SYSUT1   DD  DSNAME=INPUT,UNIT=disk,
  //             DISP=OLD,VOL=SER=X13380,
  //             DCB=(BUFNO=20,RECFM=F,LRECL=2000,BLKSIZE=2000)
  //SYSUT2   DD  DSNAME=OUTPUT,UNIT=tape,DISP=(NEW,KEEP),
  //             DCB=(RECFM=FB,LRECL=2000,BLKSIZE=32000)

The job control statements are as follows:

• The EXEC statement names the IEBGENER program and specifies the virtual storage region size required. (Calculation of region size is described in Table 1.)
• The SYSIN DD statement is a dummy, since no editing is to be performed.
• The SYSUT1 DD statement identifies an input disk file. Normally, the DCB RECFM, LRECL, and BLKSIZE information should not be specified in the DD statement for an existing disk file because the information exists in the data set label in the VTOC; it is specified in this example to illustrate the contrast with the output data set. The unit and volume serial information could be omitted if the data set were cataloged. The DCB information specifies BUFNO=20 to allow up to twenty blocks to be read with each rotation of the disk, assuming the disk track will hold that many blocks.
• The SYSUT2 DD statement identifies the output tape data set and specifies a block size of 32,000 bytes. The default of five buffers should be enough to keep pace with the input.