A tape's magnetic label provides information about the tape and the data it contains. The Backup System checks each tape before it writes to it; if the label on the tape is unacceptable, the dump cannot proceed until you insert an acceptable tape in the drive. A tape's label records the following information:
· The name of the tape, indicating its contents. The name is composed of three fields that are separated by periods: fileset_family_name.dump_level.index (the dump set name with an additional tape index). The following three types of tape names are acceptable:
- The complete name in the form fileset_family_name.dump_level.index, where the fileset_family_name and the dump_level match values that you provide with the bak dump command. The index is this tape's place in the sequence of tapes used for the complete dump set; if the dump set fits on one tape, the index for that tape is the numeral 1.
- An indicator of empty, or null, created with the bak labeltape command. The Backup System replaces the null indicator with the correct name when it puts dump sets onto the tape.
- No name, indicating it is an unused tape. Again, the Backup System generates the correct name as it transfers a dump set to the tape.
· The size of the tape. Use a number and a letter (k or K for kilobytes, m or M for megabytes, or g or G for gigabytes) to indicate a size, as described in Configuring a Tape Coordinator Machine for the TapeConfig file. Because the Backup System always uses the size specified in the TapeConfig file, the size you include in the label of the tape is intended for information purposes only.
When you label a tape, you can specify its name only, its size only, or both its name and its size. When you dump data to a tape, the expiration date of the dump level at which you dump the data is copied to the label of the tape. If a tape has an expiration date that has not expired, the Backup System refuses to overwrite the tape. If the tape's expiration date has expired, or if the tape contains no expiration date, the Backup System overwrites the tape with a dump set that has an acceptable name.
It is not essential to prelabel tapes before data is transferred to them; the Backup System can use unlabeled tapes or partially labeled tapes, which are tapes that include only the name of the tape or the size of the tape. However, you may want to prelabel a tape if:
· You want to automate the backup process as much as possible. For manually loaded tape drives, if tapes are prelabeled with the correct name, the individual performing backups needs to respond to prompts only when the system requests a tape. For automated backup devices, if the tapes are prelabeled the backup process will proceed uninterrupted.
· You wish to reuse a tape, putting a different dump set on it. The Backup System will not use a tape if the label reflects the name of a different dump set or if the label contains an unexpired expiration date. Labeling a tape overwrites its expiration date, as well as its name and size.
Note: You can force the Backup System to ignore the tape label and use any unexpired tape for dumps. See topic entitled The NAME_CHECK Parameter for information about the NAME_CHECK parameter in the user-defined configuration file.
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