Managing Availability Manually

DFSMShsm provides commands to perform availability operations on volumes and on data sets. The following tasks can be accomplished by command:

Deleting expired backup versions

DFSMShsm can determine expired backup versions of data sets and delete them. DFSMShsm uses the management class attributes to determine which expired backup versions of system-managed data sets to delete. DFSMShsm uses the parameters entered with the command to determine which expired backup versions of non-system-managed data sets to delete.

Duplicating DFSMShsm tapes

Dumps by command and automatic dumps provide a way to store data at an offsite storage facility. The data can be dumped from level 0 and ML1 volumes, but not for backup and ML2 data that was written to tapes. Off site protection of data sets can be done with aggregate backup, volume dumping, TAPECOPY, or by using the duplex tape function.

Replacing DFSMShsm tapes with alternate tapes

If a DFSMShsm original backup or ML2 tape is damaged, the data from that tape can be retrieved from the alternate tape. You can request that DFSMShsm replace its inventory references to the original tape with the references to the alternate tape. The alternate tape becomes the new original tape. Thus, when DFSMShsm refers to the data that was on the original tape, the data is retrieved from the new original tape.

DFSMShsm also provides a function called disaster alternate. Disaster alternate allows for a much faster form of tape replacement than previously existed. Should a true disaster occur, you can enter a command that causes DFSMShsm to flag all existing alternate tapes as disaster alternates. Then, you can use another command to set DFSMShsm to run in disaster mode. When in disaster mode, each data set recall and recover causes an extra check of the volume record to see if a disaster alternate tape should be substituted for the original. The disaster alternate function also allows an installation to test their disaster plan much quicker than was previously possible.

Performing volume dump

During volume dump, DFSMShsm uses a DFSMSdss function to perform a full-volume dump of the entire allocated space on a level 0 or DFSMShsm-owned volume. Volume dumps can only be performed by authorized users.

Requesting Volume Backup

To request a backup of some or all data sets on a DFSMShsm-managed volume, any primary volume, or a user volume that is not managed by DFSMShsm, authorized users can enter a command that backs up an entire volume. Keywords in the command allow you to specify whether to back up every data set on the volume or whether to back up specific data sets. Although this command is available to back up every data set on the volume, using a command to perform a full-volume dump usually provides better performance. Only authorized users can enter a command to back up a level 0 volume.

Requesting data set backup

You can request a backup of a specific data set from a mounted volume. DFSMShsm backs up the data set and temporarily stores it on a ML1 volume. The data set does not have to reside on a volume managed by DFSMShsm.

For SMS-managed data sets, a management class backup attribute determines whether data sets in the management class are allowed to be backed up by command.

DFSMShsm allows up to 64 data set backups per DFSMShsm image. Data sets can be backed up directly to tape. Storage administrators can define whether tape, ML1 DASD, or both, are to be used as target output devices.

Tape takes longer from initial selection to first write than DASD, but is potentially faster in data throughput. DASD takes less time to become available because there is no mount delay, but the throughput is potentially less than it is for tapes.