volume_archive 
BRARCHIVE uses this parameter to identify the volume set to be used for the backup of the offline redo log files.
Syntax
volume_archive = <vol>|(<vol_list>)
Default value: none
Required values: names of volumes (tapes) that are to be used for a backup run. The length of the volume name is limited to 10 characters.
If you specify more than one volume, you must separate the names with commas and enclose the list in parentheses. You can also enter SCRATCH to deactivate automatic volume management.
When BRARCHIVE starts, the automatic volume management checks all the volumes in the sequence of their names in volume_archive (only volumes whose expiration period has expired are suggested for backup). The volumes are suggested cyclically.
Example
A valid volume name was found based on parameter volume_archive (that is, the expiration period for this volume has expired). The program assumes that you have mounted this volume. Once several check mechanisms have run, backup starts using that volume.
See Selecting Volumes Automatically.
The expiration period can be configured using parameter expir_period. The automatic volume management ensures that only free volumes are offered for backup, for example, those for which the expiration period has expired. As a result, you have to supply a quantity of volumes that is large enough for your selected expiration period.
Example
You perform backups once a day, one volume (tape) is required; parameter expir_period is set to 14 (each volume is locked for 14 days at a time).
In this case, you must specify at least 14 volumes to ensure that a volume is always available. Even better is to add a buffer of around 25% – for example, specifying 18 or more volume names in this case.
To deactivate the automatic volume management, use the command volume_archive = SCRATCH. In this case, you can mount any volume whose expiration period has expired. This name is then also recorded during the backup.