Standalone usually refers to non robotic drives, is standalone you refer to a volume pool, or perhaps tapes that are non robotic.
Volume pools are just groups of media for a specific purpose, eg, you might create a vol pool called Oracle for Oracle backups, whatever you want. The scratch pool is for empty tapes (optional but recommended), NONE pool is for cleaning media, oh, there is also a catalog pool for catalog backups, the rest is up to you.
Volume groups are a logical repression of location
000_00000_tld would be tapes in robot tld 0
000_00001_told would be tapes in robot tld 1
It also shows the number of different densities, if you have LTO4 drives and media, then you add LTO5 drives into robot 0, you would use different densities for these, e.g. hcart for LTO4 and hcart2 for LTO5, you would get another volume group
001_00000_tld
This shows there is another instance of a different density of drive/ media, but not what that density is.
There is a special volume group ---, this is for standalone media that have been ejected, or are not in a robot.
When a vol group becomes empty, it disappears.
