DFSMShsm provides a patch to the MCVT so that when volume dump is run, the requested block size for DFSMSdss is 32 KB rather than the DFSMSdss system-derived block size.

The 32 760 block-size value is also included in the tape label. This can be used if a following application such as a file transfer required this format. You can use this patch with DFSMSdss.

Note: DFSMSdss only supports block size of 65 520 and above. The default block size for output records that are written to tape is the optimum block size for the output device (262 144 is the maximum).

There is no patch available for DFSMShsm volume dumps with 64 KB block size. If you require this size, add TAPEBLKSZLIM=65520 to the DEVSUPxx PARMLIB member. Note that this change will affect all tape volumes for which the BLKSIZE parameter in the tape DD statement is not specified.

The PATCH command is as follows:

PATCH .MCVT.+3D4 BITS(.......1) /* change the DFSMSdss blocksize */
                                /* default to 32K.               */