What Slot Numbers Mean in a Silo

In an autochanger, Backup specifies many of the functions by a slot number; silos use this same idea. In an autochanger, there is a fixed number of slots; Backup uses the slot number to refer to the physical location of a volume. However, a silo has a variable number of slots, starting at zero when you first configure it and limited by the silo license you purchased. The fundamental identifier of a silo volume is its barcode, which is often called a "volser" in silo documentation. The volser never changes over the life of a particular volume.

When the nsrjb command displays a list of the contents of a silo, it also displays a slot number. You can use the slot number to specify which volumes to mount, unmount, label, and inventory. Volumes are not always assigned the same slot number in the silo. The slot numbers in the silo are assigned dynamically, based on the sorted order of the barcodes that have been allocated. If you allocate more barcodes that fall earlier in the sort sequence, the slot numbers of all the volumes later in the sequence change.

Because the slot number is not a perfect identifier for silo volume, operations that might change the slot number cannot accept a slot number as arguments. For example, you cannot deallocate volumes based on slot numbers, because this operation can change the slot numbers of volumes being deallocated.