Volume pools identify logical sets of volumes by usage. They are used by Vault to determine if a volume should be ejected. Volume pools for images to be transferred off site are known as offsite volume pools. When you create the images that you want to send off site, write them to media in an offsite volume pool. During a Vault job, Vault searches a robot for images that match the selection criteria. If the media that the images reside on are in an offsite volume pool, Vault ejects that media.
You need at least two dedicated volume pools such as the following:
Do not use the NetBackup volume pool for Vault media. Because the NetBackup volume pool is the default volume pool, if you use it for Vault you can send more data offsite than you want to.
More Information
About naming conventions for volume pools and groups