Example of BSAM Like Concatenation

Figure 1 shows an example of JCL for a like concatenation that is read using BSAM. The application could use QSAM instead of BSAM. QSAM does not require BLKSIZE to be coded because this tape data set on 3590 has tape labels.

Figure 1. Like Concatenation Read through BSAM

   //INPUT DD  *
           ... (instream data set)
   //      DD  DSN=D42.MAIN.DATA,DISP=SHR
   //      DD  DSN=D42.SUPPL.DATA,UNIT=(3590,2),DISP=OLD,BLKSIZE=150000

This example requires the application to use the large block interface because the BLKSIZE value is so large.

OPEN finds that the block size value for the second DD is larger than for the first DD, which normally is 80. If the second DD is for a disk data set, its maximum block size is 32 760. BSAM OPEN for the first DD uses the BLKSIZE from the third DD because it is the largest.