Object ExtWriteAction

An extension of the PmVar variable of the PmaData object for invoking an event (action) when writing a value.
Configuration windows:
ExtWriteAction Data extension configuration
If calling the onItemBeforeWrite event is enabled, then the event is triggered for this variable always closely before writing or before the change of the variable value. Unconsidered enabling for all variables can cause unnecessary utilization of the processor. For example if the object includes 1000 variables and each one has calling enabled then by writing new values into all variables of the object can cause calling the onItemBeforeWrite event 1000 times (each time with another pEvent.Item parameter value). It is also better (if it is required to react to writing or the change of the variable) to enable the onItemAfterWrite event instead of onItemBeforeWrite. Enabling onItemBeforeWrite is useful only if, for example, you need to test the written value and in a necessity to change it (to filter it). The onItemBeforeWrite property in the onItemBeforeWrite event is defined for reading and writing and thus it is possible in the event to enforce another value than the one that is really written.

If calling the onItemAfterWrite event is enabled, then the event is triggered for this variable always after writing or the change of the variable. For enabling this event similar remarks are valid for the onItemBeforeWrite event. Enabling the onItemAfterWrite is useful for variables that change their value not too ofter and then is it suitable to enable calling 'after the change'.

Caution: The onItemBeforeWrite event and the onItemAfterWrite event is not triggered if it isn't written into the variable directly, i.e. if the variable is bind to another value.

Format of saving the data extension as string:

The contents of complete data extension (all configurators) can be saved as a single string. See Format of saving the data extension as string.


- Id: see the "Data extension identifier" configurator
- BeforeWrite: see the "Event "onItemBeforeWrite"" configurator
- AfterWrite: see the "Event "onItemAfterWrite"" configurator

Pm8.03.00: Created
PROMOTIC 9.0.10 SCADA system documentation - MICROSYS, spol. s r.o.

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