Standard Transaction Group DB to OPC problem

I am having problems trying to send setup information to multiple PLCs using a Standard Transaction Group reading data from a database view. I have multiple OPC items associated to the same database field, and each of these items is connected to a different PLC (some using Igntion UA OPC, others using RSLinx).

When I specify the part number of a triggered transaction using a custom where clause, the values are retrieved from the database BUT only the FIRST OPC item associated to the field is actually updated, the rest associated to the same field keep their value. This seems to happen for every field, only the first instance is updated.

The transaction is triggered with a boolean SQLTag that is set after the PartNumber SQLTag is changed. The triggered expression items are used to send constant values to OPC items within the transaction.

The PLCs are SLCs 505 and one MicroLogix 1500 using NET-ENI. The PLC communication is okay, since I am able to write directly to the OPC tag, but the transaction is only updating OPC item attached to the first field reference.

Any idea of what is going on? :scratch:

I am using Ignition 7.6.2 with MS SQL Server 2008.


If going to multiple machines like that I’d use expression items to read once from the database. Then use multiple expression items equal to the result to populate the OPC tags.

Thanks Jordan. That was an idea I was exploring after seeing what happened. I just wanted to be sure if the configuration I made is actually possible since there is not any explicit restriction about using the same field more than once.
I checked in the logs and the constructed query is only referencing each database field once.
It would be great if someone in the support or developing team could give us some light regarding this matter.

Jordan is right, creating Expression Items is the way to do it. The OPC items are supposed to be a one-to-one relationship with columns in the DB.

Thanks Bobby, I just wanted the confirmation. I’ll keep it in mind for future Transactions.
This was the transaction I asked you about during the Advanced Training Course after the Conference.

This is a note waiting to be included in User Manual. :wink: