Looks like they will always evaluate, but not necessarily write back. From the Manual:
[code]Execution Cycle
All of the groups follow a similar execution cycle. The core evaluation may differ, but the general cycle is the same.
- Timer executes, group enters execution
- Is the group paused? Break execution.
- Is the Gateway the cluster’s master? If not, break execution. Transaction groups only execute on the master.
- Evaluate “run-always” items: OPC items, SQLTag references, and Expression items set to ignore the trigger.
- Is trigger set/active? If there is a trigger defined, but it is not active, break execution.
- Evaluate “triggered” items: Expression items not set to ignore the trigger.
- If applicable, read values from the database
- Execute a comparison between items and their targets
- Execute any writes to other Tags or the Database that result from execution.
- Report alerts
- Acknowledge the trigger, if applicable.
- 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.[/code]
Looks like #5 is what’s hanging you up.
Can this evaluation be handled by an expression SQLTag? IIRC, you can write the results to another tag.