This is a simple sequential integer index, starting at 1, used to uniquely identify each World Wide Identifier (WWID) entry in this table -- WWIDs being the globally unique identifiers typically used for Fibre Channel or storage-related device addressing. An admin or management application uses this index purely as a table key to walk through and correlate other columns (like the actual WWID value) row by row rather than as data with operational meaning on its own. For example, index value 1 might correspond to the first HBA port's WWID discovered by the device, index 2 to the second, and so on as ports are enumerated.