Positioning shuttle cars in a tape storage shuttle complex

1. An apparatus, comprising:

a tape drive occupancy module that tracks tape drive occupancy in a plurality of library strings of a shuttle complex, the tape drive occupancy indicating whether each tape drive in the plurality of library strings is one of occupied and vacant; and

a shuttle car position module that positions a set of shuttle cars in the shuttle complex based on the tape drive occupancy in the plurality of library strings,

wherein at least a portion of said modules comprise one or more of a set of hardware circuits, a set of programmable hardware devices, and executable code stored on a set of non-transitory computer-readable storage mediums.

2. The apparatus of claim 1 , further comprising:

a mounting manager module that determines when a tape cartridge is unmounted from a tape drive, wherein the tape drive is a vacant tape drive upon the tape cartridge being unmounted; and

a location module that determines a location of the vacant tape drive.

3. The apparatus of claim 2 , wherein:

the shuttle car manager module is configured to determine whether a shuttle car is present at the location of the vacant tape drive in response to determining the location of the vacant tape drive.

4. The apparatus of claim 3 , wherein:

the shuttle car manager module is configured to relocate the shuttle car to a different location in the plurality of library strings in response to determining that the shuttle car is present at the location of the vacant tape drive.

5. The apparatus of claim 4 , wherein:

the shuttle car manager is configured to select the different position based on each tape drive at the different location being occupied by a respective tape cartridge.

6. The apparatus of claim 5 , wherein:

the plurality of library strings includes a plurality of locations in which each tape drive is occupied; and

the shuttle car manager is configured to select the different position based further on a second tape drive at the different location including a least recently used (LRU) occupied tape drive.

7. The apparatus of claim 4 , wherein:

the shuttle car manager module is configured to maintain a respective current location in the plurality of library strings for each shuttle car in the set of shuttle cars in response to determining that the shuttle car is not present at the location of the vacant tape drive.

8. A method, comprising:

tracking, by a processor, tape drive occupancy in a plurality of library strings of a shuttle complex, the tape drive occupancy indicating whether each tape drive in the plurality of library strings is one of occupied and vacant; and

positioning a set of shuttle cars in the shuttle complex based on the tape drive occupancy in the plurality of library strings.

9. The method of claim 8 , further comprising:

determining that a tape cartridge is unmounted from a tape drive, wherein the tape drive is a vacant tape drive upon the tape cartridge being unmounted; and

determining a location of the vacant tape drive.

10. The method of claim 9 , further comprises:

determining whether a shuttle car is present at the location of the vacant tape drive in response to determining the location of the vacant tape drive.

11. The method of claim 10 , further comprising:

relocating the shuttle car to a different location in the plurality of library strings in response to determining that the shuttle car is present at the location of the vacant tape drive.

12. The method of claim 11 , wherein selecting the different position comprises:

selecting the different position based on each tape drive at the different location being occupied by a respective tape cartridge.

13. The method of claim 12 , wherein:

the plurality of library strings includes a plurality of locations in which each tape drive is occupied; and

selecting the different position comprises selecting the different position based further on a second tape drive at the different location including a least recently used (LRU) occupied tape drive.

14. The method of claim 11 , further comprising:

maintaining a respective current location in the plurality of library strings for each shuttle car in the set of shuttle cars in response to determining that the shuttle car is not present at the location of the vacant tape drive.

15. A computer program product comprising a computer-readable storage medium including program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:

track tape drive occupancy in a plurality of library strings of a shuttle complex, the tape drive occupancy indicating whether each tape drive in the plurality of library strings is one of occupied and vacant; and

position a set of shuttle cars in the shuttle complex based on the tape drive occupancy in the plurality of library strings.

16. The computer program product of claim 15 , wherein:

the program instructions further cause the processor to determine that a tape cartridge is unmounted from a tape drive;

the tape drive is a vacant tape drive upon the tape cartridge being unmounted; and

the program instructions further cause the processor to determine a location of the vacant tape drive.

17. The computer program product of claim 16 , wherein the program instructions further cause the processor to:

determine whether a shuttle car is present at the location of the vacant tape drive in response to determining the location of the vacant tape drive.

18. The computer program product of claim 17 , wherein the program instructions further cause the processor to:

relocate the shuttle car to a different location in the plurality of library strings in response to determining that the shuttle car is present at the location of the vacant tape drive; and

maintain a respective current location in the plurality of library strings for each shuttle car in the set of shuttle cars in response to determining that the shuttle car is not present at the location of the vacant tape drive.

19. The computer program product of claim 18 , wherein the program instructions further cause the processor to:

select the different position based on each tape drive at the different location being occupied by a respective tape cartridge.

20. The computer program product of claim 17 , wherein:

the plurality of library strings includes a plurality of locations in which each tape drive is occupied; and

selecting the different position comprises selecting the different position based further on a second tape drive at the different location including a least recently used (LRU) occupied tape drive.