Citect SCADA 7.20 – Trend Only Showing Real-Time, No Historical Data.

Not sure what you mean by "... with logging enabled" and "Log Device is set to 'Trend' ". I can't recall these properties being a part of the trend tag configuration (although I haven't touched v7.20 in over ten years).
It should be sufficient to define a Trend Tag that refers to a Variable Tag in its Expression field.

Do you see trend files being created in the Data folder? There should at least appear files that are named "<Trend Tag>.HST" and also files called *.000, *.001, etc.

As 7.20 is a very old version that does not officially support modern environments (for example current Windows versions), I would indeed recommend upgrading to a newer version. I would strongly advise to consider a version that is currently in active Support, such as v2023R2, and I would certainly avoid v7.30 if you can.

Thanks for your reply!

Yes — I can confirm that the data files are being generated. I can see the .HST files and also files like .000, .001 in the Data folder.

However, when I try to view the trend, it only shows real-time data. I'm unable to scroll back or view any historical data in the trend display.

I've double-checked the Trend Tag configuration and everything seems to follow the manual.

Do you think this issue could still be related to version limitations (v7.20)? Or is there something else I might be missing in the configuration?

Thanks for your reply!

Yes — I can confirm that the data files are being generated. I can see the .HST files and also files like .000, .001 in the Data folder.

However, when I try to view the trend, it only shows real-time data. I'm unable to scroll back or view any historical data in the trend display.

I've double-checked the Trend Tag configuration and everything seems to follow the manual.

Do you think this issue could still be related to version limitations (v7.20)? Or is there something else I might be missing in the configuration?

The Device in your screenshot causes a major conflict with your Trend Tag. Both configurations will result in the creation of history files (*.000, *.001, etc.) with the exact same names, but totally different content (binary trend data vs.dBaseIII records).

I'm still not sure why you have defined this device. It is NOT needed for normal trend operation.

Thanks for pointing that out.
I’ve now removed the unnecessary Device configuration and kept only the Trend Tag setup as you suggested.

After restarting the runtime, the conflict with the historical files (*.000, *.001) should no longer occur. I’ll monitor the system to confirm that the historical data loads correctly now.

Really appreciate your help.

Best regards,
Sasin

No problem. I hope it will fix things for you.

Please also note Erik's post about reviewing your trend tag's Period, Time, and No. Files parameters (and possibly also the Sample Period).
After any changes to these trend tag properties it is necessary to delete your trend files from the data folder. On a restart of the trend server new files will be created, with the correct layout.