Specifying the device type for backup of the control data sets

The control data sets and journal data set can be backed up to either DASD or tape. Both DASD and tape have certain advantages in relation to each other. In deciding whether to use DASD or tape for backing up your control data sets and journal data set, consider the following factors:

Mounting: You do not have to mount DASD. For tape backup, you must mount a tape for each control data set and the journal.
Allocation: With DASD, you do not have allocation problems that are caused by no available drives. With tape, the allocation request for a scratch tape fails if no tape drives are available.
SMS-managed: With DASD, the backup copies of your control data sets can be SMS managed.
Preallocation: With tape, you need not preallocate backup data sets.

Whether you back up the control data sets to DASD or to tape, DFSMShsm issues messages ARC0742I and ARC0743I for each data set that is backed up. If the backups are in nonparallel mode, the messages are issued in pairs. However, if the backups are in parallel mode, all of the ARC0742I messages may be issued before the first ARC0743I message is issued. Parallel processing makes it possible to start all the backups before the first backup is completed.

If you decide to back up the control data sets and journal data set to DASD, you must preallocate the data sets. Also, allocate the different versions of the backup data sets on different volumes. This better ensures that you can recover your backup versions.

In the example system, backup is shown going to DASD. Therefore, the command that is added to the ARCCMDxx member in processing unit 1 is modified as follows:

SETSYS CDSVERSIONBACKUP(DATAMOVER(DSS) -
   BACKUPCOPIES(3) -
   BACKUPDEVICECATEGORY(DASD) -
   BCDSBACKUPDSN(BHSM.BCDS.BACKUP) -
   MCDSBACKUPDSN(BHSM.MCDS.BACKUP) -
   OCDSBACKUPDSN(BHSM.OCDS.BACKUP) -
   JRNLBACKUPDSN(BHSM.JRNL.BACKUP))

Unlike backup of user data sets, backup of the control data sets must be to only one kind of I/O device. You cannot use a mixture of DASD and tape.