Polling vs report-by-exception in SCADA systems - Quick Revision & Key Differences

Recall & Review

beginner

What is polling in SCADA systems?

Polling is a method where the central system regularly asks each device for its status or data at fixed intervals.

beginner

What does report-by-exception mean?

Report-by-exception means devices only send data or alerts when something changes or an event happens, instead of sending data all the time.

intermediate

Which method reduces network traffic: polling or report-by-exception?

Report-by-exception reduces network traffic because data is sent only when needed, not continuously.

intermediate

What is a downside of polling?

Polling can cause unnecessary network load and delays because it asks for data even if nothing has changed.

intermediate

Why might report-by-exception be better for real-time alerts?

Because devices send updates immediately when something changes, report-by-exception allows faster response to important events.

In polling, how does the central system get data?

A By regularly asking devices for data

B Devices send data only when something changes

C Data is sent randomly

D Data is never sent

Polling means the central system asks devices for data at set times.

Which method sends less data over the network?

A Polling

B Report-by-exception

C Both send the same amount

D Neither sends data

Report-by-exception sends data only when needed, reducing network traffic.

What is a disadvantage of report-by-exception?

A It can miss data if no events happen

B It always sends data even if unchanged

C It causes high network load

D It requires constant polling

If no events happen, report-by-exception may not provide regular updates.

Polling is best described as:

A Devices push data when needed

B Data is sent only on errors

C No data exchange

D Central system requests data regularly

Polling means the central system asks for data at intervals.

Which method allows faster reaction to changes?

A Neither

B Polling

C Report-by-exception

D Both are equally fast

Report-by-exception sends updates immediately when changes occur.

Explain the difference between polling and report-by-exception in SCADA systems.

Think about who initiates data sending and when.

What are the advantages and disadvantages of polling compared to report-by-exception?

Consider network load and data timeliness.