The HSM usage pattern requires special consideration for GFTAVMA. For these data sets only, the cumulative gigabytes transferred represents the total amount of data written for output only over the entire sample studied. For all other data sets, GFTAVMA uses the last quantity of data written as the current size of the data set. If there are no writes, the size of the data set is the amount of data transferred in the last open for output.

If migrations, recalls or backups, and recovery are the only activities occurring to the SFF data sets, GFTAVMA can measure how well DFSMShsm is using tape. However, if there is tape RECYCLE activity during the time studied, these opens, reads, and writes are added into the cumulative totals shown for the data set. Further, tape RECYCLE processes smaller amounts of data per read or write, which deflates the average megabytes/volume statistics.

DFSMShsm also uses various other utility and backup data sets, such as control data set backups, that are written to tape. Since DFSMShsm has special data set uses and sizes, GFTAXTR categorizes all DFSMShsm data sets as USAGE(HSM).