Transaction group - Update mode: DB to OPC


I’ve set my block transaction group to trigger after value change and I’ve chose update mode to be DB to OPC. When I write a value to DB by PLSQL, I see in Database Query Browser that the value changed, but the tag in Designer remains still. After changing value of one of the other tags, the value I’ve sent via PLSQL is written to the tag.

This doesn’t happens when I use timer execution, but I want the values to be updated on-change.

Thanks for your help.

There’s no notification from JDBC to Ignition that a row in a table changed. So there’s nothing Ignition can use to implement your idea. Tables that change outside Ignition need to be polled for Ignition to see the changes. That’s why it works with no trigger, and use of no trigger is the right answer.

So it’s not possible to create triggered by on-change bi-directional communication between SCADA and Database?

Not for changes coming from the database. Those can’t be seen until you’ve queried the database for the latest data. The trigger of a transaction group is what causes the query to happen.

Note that it isn’t a question of bidirectional or not. Not even unidirectional from the the DB can be triggered by changes in the DB.

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