Expression Expression Delta Interval

1.3.6.1.2.1.90.1.2.1.1.6

Sampling interval for objects in this expression with expObjectSampleType 'deltaValue'. This object has no effect if the the expression has no deltaValue objects. A value of 0 indicates no automated sampling. In this case the delta is the difference from the last time the expression was evaluated. Note that this is subject to unpredictable delta times in the face of retries or multiple managers. A value greater than zero is the number of seconds between automated samples. Until the delta interval has expired once the delta for the object is effectively not instantiated and evaluating the expression has results as if the object itself were not instantiated. Note that delta values potentially consume large amounts of system CPU and memory. Delta state and processing must continue constantly even if the expression is not being used. That is, the expression is being evaluated every delta interval, even if no application is reading those values. For wildcarded objects this can be substantial overhead. Note that delta intervals, external expression value sampling intervals and delta intervals for expressions within other expressions can have unusual interactions as they are impossible to synchronize accurately. In general one interval embedded below another must be enough shorter that the higher sample sees relatively smooth, predictable behavior. So, for example, to avoid the higher level getting the same sample twice, the lower level should sample at least twice as fast as the higher level does.