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All of the groups follow a similar execution cycle. The core evaluation may differ, but the general cycle is the same.
| 1) | Timer executes, group enters execution |
| 2) | Is the group paused? Break execution. |
| 3) | Is the Gateway part of a redundant pair? If so, is it active? If not active, break execution. Groups only execute on the active node. |
| 4) | Evaluate "run-always" items: OPC items, SQLTag references, and Expression items set to ignore the trigger (or placed in the "run always" section of the configuration window). |
| 5) | Is trigger set/active? If there is a trigger defined, but it is not active, break execution. |
| 6) | Evaluate "triggered" expression items. |
| 7) | If applicable, read values from the database |
| 8) | Execute a comparison between items and their targets |
| 9) | Execute any writes to other Tags or the Database that result from execution. |
| 11) | Acknowledge the trigger, if applicable. |
| 12) | Write handshake value, if applicable. |
If an error occurs at any stage besides the last stage, execution will break and the failure handshake will be written if configured. The group will attempt execution again after the next update rate period.
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