DFSMShsm typically transfers large amounts of data. Therefore, GFTAXTR needs to separate these data sets. If the DFSMShsm data sets are placed in active or backup categories, they can drastically influence any averages, totals, or summary information, which might cause the volume mount analyzer to draw inaccurate conclusions about those categories.

The most common usage of tape by DFSMShsm is the single-file format (SFF) data sets used for migration level 2 or backup.

When migrating or backing up user data sets to tape with SFF, DFSMShsm places data in blocks of 16384 bytes in these large, multivolume data sets. The SFF data sets are named hlq.HMIGTAPE.DATASET or hlq.BACKTAPE.DATASET. They are not cataloged and can span up to 255 tape volumes. DFSMShsm continues writing user data sets in a single SFF data set until it is full. At that point, DFSMShsm opens another SFF data set with the same name.