A unique value used by this host system to identify this
conceptual row in the 'xcmHrDevAlertTable'.
Usage: Conforming implementations SHALL NOT 'reuse' values of
'xcmHrDevAlertIndex' until its' 32-bit value wraps. Even in
the case of eventual wrap, the entries SHALL be strictly
sequenced by the associated value of 'xcmHrDevAlertDateAndTime.'
Usage: When an event causes an alert on several devices, all
such alerts SHALL have the same 'xcmHrDevAlertIndex.'
Usage: Conforming implementations are strongly encouraged to
preserve the last used value of 'xcmHrDevAlertIndex' across
system power cycles.