SUBSYS DD Parameter › Special Considerations When Using SUBSYS › DCB Information When Using SUBSYS

DCB Information When Using SUBSYS

When you code the SUBSYS parameter for the CA Compress subsystem, you can code the other parameters just as you normally would. However, you must always code the DCB parameters for non-VSAM data sets (BLKSIZE, LRECL, and RECFM), even if they already exist (DISP=SHR or DISP=OLD).

There are three restrictions on BLKSIZE and LRECL which you must observe when using CA Compress:

• The BLKSIZE must be at least 12 bytes greater than the LRECL.
• The LRECL cannot be larger than 32,744 bytes.
• Do not code BLKSIZE=0 in order to invoke System Determined Blocksize.

Compression can cause a record to grow by up to 8 bytes, 12 if it was originally fixed length. In order to prevent the logical record length from exceeding the block size, and to prevent the block size from exceeding the maximum value, the BLKSIZE and LRECL restrictions must be adhered to.