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Types of Backup Media

CA VM:Backup backs up data from minidisks and file spaces to disk or tape. CA VM:Backup writes all backups as standard label data sets. It also verifies the volser and tape expiration date to prevent an incorrect tape from being used or to protect tapes from being overwritten inadvertently.

If you use CA VM:Tape, CA VM:Backup will deny the mount request for any tape selected by CA VM:Tape that is part of an unexpired CA VM:Backup catalog or owned by CA VM:Archiver.

Physical Tapes

As a job executes, CA VM:Backup issues mount requests that state explicitly what type of media is required.

Backup Jobs

For backup jobs, CA VM:Backup handles tapes as follows:

Restore Jobs

For restore jobs, CA VM:Backup performs the following tasks in this order:

  1. Identifies the files to be restored
  2. Locates the volsers of the tapes containing those files
  3. Issues a request to have the tapes mounted

DASDtapes

CA VM:Backup has complete control over the management of DASDtapes. DASDtapes are the CMS files created when data is backed up to disk instead of to physical media. CA VM:Backup restores data from DASDtape without operator intervention.

During a backup, CA VM:Backup automatically selects a tape from expired or unused DASDtape volsers. If all available volsers have been used, CA VM:Backup either asks you to provide the volser of the next DASDtape to be used in the job, or CA VM:Backup places the backup job on hold, depending on how the system administrator has set up tape handling at your data center.

Tape Streams

CA VM:Backup can write data to multiple tape drives in a single backup by dividing the minidisks and file spaces being backed up between two or more tape streams. The number of tape streams used in a backup is determined by the CA VM:Backup system administrator on the backup job template file or by the STREAMS option on the CA VM:Backup SUBMIT command. CA VM:Backup can manage a maximum of 15 tape streams at a time.

Tape Copies

Tape copies are duplicate tapes created at the same time on different drives. They are useful for offsite or vault storage, or when your system is recovering from tape I/O problems. Up to four copies can be created in addition to the primary (or first) tape.

The data written to each tape copy is identical. If one tape is longer than the other, the extra footage on the longer tape is not used.

The only differences between the tapes are the volser in the VOL1 label, certain control information in the header and trailer labels, and optionally, different expiration dates and data set names. Media types (that is, cartridges, or enhanced-capacity cartridges) can also differ among tape copies. During a restore, any copy can be used in place of the primary tape or any corresponding copy.