Buying this licenses will resolve this kind of error:
[61:17102] Not enough licenses "Direct attached tape drive for Windows / NetWare / Linux".
And it will also resolve this very similar error:[61:17102] Not enough licenses "Tape drive for SAN / all platforms". Session is waiting for some of devices to get free.
What's going on is that you already have a cell manager license for (HP Data Protector, HPE Data Protector, Omniback), and that lets you run one tape drive at a time even before you buy anything else. But now you want to have a second tape drive being written to at the same time, or a third or a fourth, or whatever ...
This is the same license regardless of whether this is for LTO (any generation, including LTO-5, LTO-6 or LTO-7), Ultrium, DLT, DAT, DDS.
If you are using a virtual tape library where you can have many virtual drives, you might want to compare the price of buying a few TB of advanced-backup to disk instead.