The amount of space that you allocate for your CDS and journal backup copies depends on the size of the CDS or journal data set being backed up. Ensure that all DASD backup data sets have the same size as their corresponding control data sets or journal data set.

Example: For a backup data set of the MCDS, allocate a DASD backup data set that is the same size as the MCDS. For a backup data set of the BCDS, allocate a DASD backup data set that is the same size as the BCDS, and so forth.

If the journal is allocated as a large format sequential data set, larger than 64K tracks, and you are backing up to DASD, you must preallocate the journal backup data set as a large format sequential data set, which is large enough to contain a copy of the original large format sequential journal.

You do not have to be concerned about the size of the tape backup data sets, because DFSMShsm can span up to 18 tapes for control data set and journal data set backup copies.