Chapter 2. IBM Open Systems Tape Library sharing and partitioning 79
In Figure 2-66 we again show the detailed view of the logical library. The drive element
addresses are the same as before, but the storage element addresses were changed.
Because it is seen as the first logical library, the storage element addresses begin with 1025.
With ALMS, the physical limitation of 175 cartridge slots is removed, and we have assigned
160 slots to this one logical library. There is now also a listing of the default 30 Virtual IO
Figure 2-66 Detailed Information after ALMS enabled
2.3.4 Using ALMS
Because ALMS virtualizes the SCSI element addresses of the cartridge slots, some library
commands do not generate a physical action on the library. If a move media command is
issued the library replies with a new SCSI element address even though the cartridge was
physically not moved.
Note: On i5/OS the SCSI element address is administered by the IOP and thus
transparent for the user.
80 Implementing IBM Tape in i5/OS
For example, suppose that we want to move the cartridge stored in Frame 1, Column 3, Row
13 (see Figure 2-67) from SCSI element address 1128 to a vacant SCSI element address.
Use the menu selection Cartridges → Data Cartridges, and select from drop-down Move to
move the cartridge.
Figure 2-67 Inventory before move medium
A pop-up window lets you choose your move method. We select first empty slot as in
Figure 2-68 Select move method
Chapter 2. IBM Open Systems Tape Library sharing and partitioning 81
Now, we again check the inventory of the library (see Figure 2-69). We see that the SCSI
element address has changed to 1129, but the cartridge is still in the same physical location:
Frame 1, Column 3, Row 13.
Figure 2-69 Inventory after moving cartridge
On a library without ALMS, you have to run a library inventory every time after moving some
cartridges manually to get the application in a state consistent with the library. With ALMS this
might no longer be required, as ALMS always tries to assign the same SCSI element address
to the cartridge, even though the cartridge was moved manually.
Because ALMS is based on the affinity between VolSer (barcode label) and the reported
SCSI element address, you have to make sure that the barcode label is readable. The library
tries to keep the same SCSI element address for an unreadable barcode label if this cartridge
is stored in the same physical slot. But, if the cartridge was moved manually, and the library
does an inventory, a cartridge with an unreadable barcode label is placed in an unassigned
The same is true if you work with unlabeled cartridges (no barcode label). As long as you do
not move this cartridge manually, the library tries to assign a SCSI element address. If you
move such a cartridge manually, the cartridge is placed in an unassigned status.
The same happens with cartridges having duplicate barcode labels. Anyway, using duplicate
barcode labels is generally not supported, and can easily lead to confusion.
It is possible that the storage capacity of the library, as reported by each logical library, might
exceed the physical storage capacity of the library. As such, it is possible to run out of storage
space while still reporting available space to a host. SNMP and operator panel messages
notify the customer as the library approaches near full capacity. In addition, if cartridges are
placed in the I/O station when a library has reached its capacity, the cartridges are marked
inaccessible to all hosts to prevent the condition where the host tries to move the cartridge to
storage that does not really exist.
82 Implementing IBM Tape in i5/OS
When ALMS is enabled, auto clean is automatically enabled, and there is no mechanism to
disable it. Cleaning cartridges are never associated to a logical library, so there is no host
awareness that they exist in the library.
Static partitioning cannot be used when ALMS is enabled. The partitioning for the entire
library is either static or dynamic.