You can use the debug mode of operation to monitor the effect of DFSMShsm on your computing system. You specify the DEBUG parameter of the SETSYS command to prevent data set movement or deletion from occurring during volume processing.

In debug mode, DFSMShsm simulates volume processing without moving data or updating the control data sets. Messages about volume processing are printed in the activity log and, optionally, at the console. This allows you to monitor the data sets and volumes that are managed if you have specified the NODEBUG parameter of the SETSYS command. As a result of these simulated volume processes, you can determine which data sets you want to prevent DFSMShsm from processing.

To use the debug mode, decide which volumes you want DFSMShsm to manage. First, identify which volumes in your computing system qualify as level 0 volumes. Candidates for level 0 volumes are those volumes containing data sets that should be processed by space management, backup, and dump. Then, based on the number of level 0 volumes that you want DFSMShsm to manage and the amount of data set activity you anticipate on the level 0 volumes, you can decide how many migration level 1, migration level 2, daily backup, spill backup, and dump volumes your computing system requires. After you add these volumes to DFSMShsm, regularly monitor the use of space on all the volumes managed by DFSMShsm so you can add more volumes as your computing system needs them.

After you decide which volumes DFSMShsm is to manage, run DFSMShsm in debug mode. When you are satisfied that the data sets and volumes are being managed as you would like them to be, specify the NODEBUG parameter of the SETSYS command to enable DFSMShsm to actually begin processing the data sets and volumes. You can use this gradual conversion procedure whenever you put additional volumes under DFSMShsm control.

If you issue ABACKUP or ARECOVER commands while DFSMShsm is in debug mode, the commands operate as though you have used the VERIFY parameter.

Data sets that are indicated as migrating or backed up in debug mode can be recalled and recovered with a message that the recall or recovery occurred.