Discrete attribute runtime behavior: statistics

The following describes the Discrete statistics runtime behavior:

• If the input value is BAD or UNCERTAIN quality, then all calculated values quality is set to UNCERTAIN. The calculations will continue and the values quality will remain UNCERTAIN until the Reset attribute is set TRUE and the quality of the input value is GOOD.

• Upon deploy of a User Defined instance when the InputSource is BAD, the quality of all calculating statistics is INITIALIZING.

• If AccessMode is Output, the statistics will accumulate based on what you used to poke the attribute.

• If AccessMode is Input or InputOutput, the statistics will accumulate based on the InputSource.

• If the Field Attribute value quality is INITIALIZING, the quality of the calculated statistics will be set to UNCERTAIN and the calculations will continue.

  Note: Enabling Discrete statistics increases system resources utilization due to the checkpointing of all calculated statistical values. Since a majority of these calculations are updated on every execution cycle of the engine, they are checkpointed on every execution cycle.

When calculating TimeSinceLastTransition:

• If there is no change in the input value, the TimeSinceLastTransition elapsed time value increments to show the new elapsed time value since the last value change.

• If there is a change in the input value, the TimeSinceLastTransition elapsed time value resets.

On failover:

• All calculated statistics attribute values are retained and the quality is set to UNCERTAIN.

• The calculated statistics will continue when the quality of the Field Attribute is GOOD or UNCERTAIN.