Media overwrite options set the order in which Backup Exec searches for overwritable media. When Backup Exec searches for overwritable media for a backup job, it searches for either scratch media or media that has an expired overwrite protection period.
You are prompted to select one of the following types of media that you want Backup Exec to use first:
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Overwrite scratch media before overwriting recyclable media contained in the targeted media set.
If you choose to overwrite scratch media before recyclable media, more media may be required for the same number of jobs, but the recyclable media may be preserved longer for possible recovery.
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Overwrite recyclable media contained in the targeted media set before overwriting scratch media.
If you choose to overwrite recyclable media before scratch media, you will re-use the same media more frequently than if you choose to overwrite scratch media before recyclable media.
In a device pool, Backup Exec selects the oldest recyclable media in all of the devices in the device pool to use first.
In a robotic library, Backup Exec selects the oldest recyclable media in the library to use first. If the robotic library is partitioned, Backup Exec searches for the oldest recyclable media in the targeted partition only.
The following table describes the order in which Backup Exec searches for media to use for an overwrite job, depending on the combination of the overwrite protection level and the media overwrite option you select.
Table: How Backup Exec searches for overwritable media
In addition to setting overwrite protection levels, you must set overwrite options, which set the order in which Backup Exec searches for overwritable media.
The most obvious candidates for backup jobs requiring overwritable media are scratch media and recyclable media (media with expired overwrite protection periods). These are the first types of media for which Backup Exec searches when a backup requires media to overwrite. The search pattern is different according to whether you have chosen Full, Partial, or None. The media indicate that a type of media set is examined for availability.