The Scan, Alarm, and Control program (SAC) is a system application that runs on a SCADA node. This program is responsible for executing the logic of the database chains. SAC performs the following functions:
- Retrieves data from various data sources
- Translates the data into the format expected by the database
- Checks the data against the alarm limits and generates alarm messages
- Executes the control logic
- Detects exceptions
- Makes requested writes to the database
Each database chain also contains the information that determines whether SAC processes the chain based on time-based, exception-based, or one-shot processing. A node can perform both time-based and exception-based processing simultaneously. This feature gives you the ability to use the best processing strategy for each data point in your system.
