DFSMShsm

Unlike other non-VSAM data sets that can be opened and closed repeatedly throughout the day, some file systems are often mounted for several days or weeks at a time, with the individual file members inside opened as needed. Normally, DFSMShsm's automatic backup (AUTOBACKUP) processes file systems at most once per mount, so a file system mounted for a week would only have one backup taken for that week. For some applications, that might not be frequent enough. Fortunately, DFSMShsm provides some alternatives to ensure that backups are taken more frequently.

An SMS-managed storage group can be defined with guaranteed backup frequency (GBF). For example, if GBF=3 days, then if a backup has not been taken for a particular data set in the last three days, a fresh backup is taken, whether the file has been updated or not. Since this applies to all data sets on a storage group, some customers have placed their file systems into a unique storage group with a specification of GBF=1, so as not to affect other types of data.
Backups once a day might not be frequent enough. DFSMShsm provides commands to invoke backups to be taken, independent of the standard autobackup cycle and window. The BACKVOL TOTAL command can be used to back up all the files on a single DASD volume, a list of DASD volumes, a single storage group, or a list of storage groups. This command can be invoked from a job scheduling package such as Tivoli® Workload Scheduler for z/OS®, or console automation package, such as Tivoli NetView® for z/OS.
If file systems are intermixed on the DASD volumes with other data set types, you might want to back up the file systems individually. You can use the DFSMShsm command BACKDS to back up a single data set, or a set of data sets that match a particular mask filter. The DFSMShsm batch program ARCINBAK can be used to back up a list of data sets that support JCL backward reference and variable substitution. DFSMShsm also provides ABACKUP, which identifies which file systems are part of a single aggregate list, and backs these up as a single entity. You can invoke both the BACKDS and ABACKUP commands from job scheduling or console automation software.
If the application was developed in-house, you can modify it to perform the backups internally. It might be able to perform its own quiesce process, or coordinate time stamps with its own transactional log. DFSMShsm provides the ARCHBACK assembler macro interface.

If a file system is mounted for read/write to a single MVS™ image, back it up by DFSMShsm from the MVS image that has it mounted. For automatic backup, you might need to designate host affinity by specifying a system name associated with AUTOBACKUP for each storage group. For command-initiated backups, you might need to ensure that the commands or batch jobs are issued to the correct MVS image.

If the file system being dumped by DFSMShsm is currently mounted as read/write, then this file system can only be dumped from the system on which it is mounted. If the file system is mounted as read-only or is in a sysplex (mounted read-only or read/write), then it can be dumped from any system that has access to it.

If you use DFSMShsm, you must define a user ID for the DFSMShsm address space. For DFSMShsm to access the file systems, it must run under a user ID that is set up for access to a z/OS UNIX system. When you set up this access:

The default group for the DFSMShsm user ID must have an OMVS segment defined and a group ID associated with it.
The home directory must be the root file system.