|A gauge associated with a performance measurement in
a previous 15 minute measurement interval. In the case
where the agent has no valid data available for a
particular interval, the corresponding object instance is
not available and upon a retrieval request a corresponding
error message shall be returned to indicate that this
instance does not exist.
Let X be an object with HCPerfIntervalCount syntax.
Let Y be an object with HCPerfCurrentCount syntax.
Let Z be an object with HCPerfTotalCount syntax.
Then, in a system supporting a history of n intervals with
X(1) and X(n) the most and least recent intervals
respectively, the following applies at the end of a 15
- discard the value of X(n)
- the value of X(i) becomes that of X(i-1)
for n >= i > 1
- the value of X(1) becomes that of Y.
- the value of Z, if supported, is adjusted.
This count represents a non-negative integer, which
may increase or decrease, but shall never exceed 2^64-1
(18446744073709551615 decimal), nor fall below 0. The
value of an object with HCPerfIntervalCount syntax
assumes its maximum value whenever the underlying count
exceeds 2^64-1. If the underlying count subsequently
decreases below 2^64-1 (due, e.g., to a retroactive
adjustment as a result of entering or exiting unavailable
time), then the value of the object also decreases.
Note that this TC is not strictly supported in SMIv2,
because the 'always increasing' and 'counter wrap'
semantics associated with the Counter64 base type are not
preserved. It is possible that management applications
which rely solely upon the (Counter64) ASN.1 tag to
determine object semantics will mistakenly operate upon
objects of this type as they would for Counter64 objects.
This textual convention represents a limited and short-
term solution, and may be deprecated as a long term
solution is defined and deployed to replace it.