Can two tags point to the same tag history

[wschauer]

We have some that paths that are nested into folder and UDT’s a few layers deep. [Production]Site/Cable/Line1/Extruder/Zone1_HTR/TempPV.

Our process group would like to have a single folder to pick tags from to trend.
IE. Site/Line1/ProcessParameters/ExtruderZone1Temp….

Is it possible to point two tags to the same historical data? This way we don’t duplicate tag history but we allow the process folk to see all their tags in a single folder while we still save the tag history in its proper location.

[robertm]

I honestly think that was the idea behind reference tag types, but it never really came to fruition. Your question has been asked several times over the years, but I have not seen a resolution:

Purpose/Function of Reference Tags

Hey! Was just wondering about the planned functionality/purpose of “reference tags” – are they any different than pointing an expression tag at the tag to be referenced? I was sort of expecting these to work like “Tag Aliases” e.g. would not have to specify datatype, other metadata – all would be pulled from the reference… but it does not seem like this is the case thus far. Was also wondering if the reference tag would automatically link to the reference tag’s history (if configured). Thanks…

[MMaynard]

You can duplicate the tags into the ProcessParameters folder and then enable history on the tags there. Don’t enable it on the tags on the original path.

Duplicating tags like this will not cause any extra load on the PLC as Ignition sees them as being duplicated and will not double subscribe them.

[robertm]

Wouldn't that create orphaned historical IDs and break any sparkline/charts bound to the original tags?

[lrose]

Yes, you would have to go into any active partitions and update the tagid's to the new tagid's before the new paths would point to the old data. Any future data would be fine though.

@wschauer The short answer to your question is no. Each tag path is given a unique ID and the data is stored by that ID. Two different paths can not share the same ID.

[MMaynard]

Yes it would.

But it will be better to do it this way and then update the partitions vs storing duplicate values for the same source path.

The lack of Historical Tag Alias is what caused us to write out own tag display system that uses the tooltip field from the tags for operator selection, vs the full tag path. This way we can group and display whatever name the operators need to recognize what the tag actually is.

[pturmel]

I would not move or duplicate the tags. This is a UI issue that should be handled by preparing a custom tag selection UI, that displays desired groups of tags in flat lists.

[pascal.fragnoud]

I was gonna suggest just that.
You can even have a DB table storing different tags lists for different profiles.

Then you just show these particular tags to the corresponding profile.
Don't forget to disable the powerchart's tag browser if you don't want users to access tags that aren't for them.

[wschauer]

Thanks for all the feedback.

I think the consensus is to build a separate flat UI specifically for this purpose. Which actually allows me to add some custom filtering as well so worth the effort. Thanks

[Nol]

@pascal.fragnoud

I was gonna suggest just that.
You can even have a DB table storing different tags lists for different profiles.

Then you just show these particular tags to the corresponding profile.
Don't forget to disable the powerchart's tag browser if you don't want users to access tags that aren't for them.

That’s what I ended up doing. Added button on every faceplate they can save a pv to their QuickPoints list and then in the trend page they can select QuickPoints and it displays a list of the tags they’ve personally saved. They can select what point they want and hit add to trend. The list auto saves to the database along with their username so it recalls their list every session when they login. Also is handy since they can configure their own lists and then when they’re in the field on iPads easily trend what they want.