System Programmer Reference › Managing Tape and DASD Resources › Tape Formats

Tape Formats

When running a backup job, CA VM:Backup always writes the tape data as a single physical file on the output tape or tapes. Thus system backup jobs typically create single dataset, multi-volume tapes. When backing up data for CA VM:Archiver, the output dataset is appended on the end of the last output tape. This results in multiple datasets on multiple volumes. During an MPC job, CA VM:Backup copies data from multiple datasets on multiple volumes to a new output dataset which, if necessary, spans more than one volume.

CA VM:Backup uses standard label tapes for backup data whether DASDtapes or physical tapes are used. CA VM:Backup always checks the labels, which contain the volser, tape expiration date, and a description of the type of data records on the tape, to prevent anyone from mounting an incorrect tape and inadvertently overwriting valid data.

When a backup or MPC job uses more than one tape, by default CA VM:Backup uses the standard labels to chain the tapes together. The trailer label of each tape contains the volser of the next tape used in the job. The header label identifies the volser of the previous tape. For a backup job, the header labels of the first tape in each stream contain the volsers of the first tape used in each of the other streams.

If your site uses automatic cartridge loaders (ACLs) and you want to pre-load general scratch tapes, you may want to prevent CA VM:Backup from writing tape chaining information in backup tape labels. For information, see Tape Chaining.

You must initialize physical tapes before using them in a backup or MPC job. You can use the WVOL1 operand of the CMS TAPE command to initialize tapes; see the appropriate IBM documentation for more information.

The default data set name in the tape label CA VM:Backup creates is based on the tape copy number. For example, the default data set name can be VMBACKUP.PRIMARY or VMBACKUP.COPY1. You can override the default data set name on each tape copy by updating the tape guidelines in the backup or MPC job template file. For more information, see "OUTPUT record" in the Template Programming Interface Guide or "Specifying Tape Guidelines for Backup Jobs" in the Administration Guide.