Apparatus and associated method for loading a first tape cartridge into a tape drive, the first tape cartridge formatted to include a user data partition and also to include an index partition, different than and sized smaller than the user data partition, to store an index that self-describes user data designated to the user data partition and to also store non-index data, then reading the non-index data in the index partition of the first tape cartridge to self-describe a second tape cartridge different than the first tape cartridge.