Excessive Change of Value (COV) Rate

Overview:

The "Excessive Read Rate" diagnostic fails when data is being read or polled at an unusually high frequency. Excessive reads can put unnecessary strain on the Operational Technology network, impacting its performance, and potentially leading to inefficiencies or malfunctions.

Causes:

• Overpolling: Overpolling occurs when a building automation system requests data from sensors or devices more frequently than necessary, leading to redundant or excessive readings.
  
• Misconfiguration: Incorrectly configured settings may unintentionally set a very high read rate for a data point or sensor.
  
• Faulty Programming: Faulty or inefficient control programming can unintentionally trigger excessive data requests.

Implications:

• Network Load: Excessive read rates can generate a high volume of network traffic, affecting network performance and response times.
  
• Resource Consumption: Frequent data polling can consume unnecessary system resources, leading to inefficiencies and affecting overall system stability.

How to fix it:

• Use OptigoVN Site Scope(s) to identify the addresses of all devices with excessive COV rates. Refer to our BACnet Object glossary to identify the points with excessive COVs.
  
• Configuration Review: Review and verify configuration settings for data polling rates to ensure they align with the intended requirements.
  
• Reduce Poll Rates: Set appropriate polling frequencies based on the importance of the data, the rate of change, and the system's operational needs.
  
• Optimize Control Programming: Optimize control programs and scripts to avoid unnecessary or redundant data polling.
  
• Rate Limiting: Implement rate-limiting mechanisms to prevent excessive data polling.
  
• Upgrade hardware: If polling rates cannot be reduced, consider replacing affected devices with ones with greater processing capacity.
  
• Network Monitoring: Monitor network traffic and resource usage to identify patterns of excessive read rates.
  
• Load Balancing: Distribute data requests evenly across devices and controllers to prevent resource overload on a single component.
  
• Testing: Conduct testing to ensure that the system's read rates are within acceptable limits and that data is being collected efficiently.