The following lines aim to see how the Historicals work in Intouch, Who records the data? Where? How is that information stored?
To start answering all these and more questions, we will begin where all the configuration is in the same Intouch Stand Alone project, without dependencies on the Historian Server.
This was one of the new features of version 2020, to configure the Historian settings within the Intouch project itself, to avoid having to do this configuration externally.
The first thing we did to clarify concepts was to create a project in Intouch, and without any prior configuration, run the Runtime.
As a result, we can see that when running the Runtime, the following applications automatically start in parallel.
As a first conclusion, regardless of whether we have defined any variable to log or whether we have a Historical object, the Intouch Historical Data Server application runs in parallel and is executed by the viewer itself.
The Intouch Historical Data Server is responsible for supplying data to the ActiveX controls that request data. Configuration based on Server - Client.
Next, we create some variables and activate the checkbox to log, this is the Log Data checkbox and another parameter related to how much data we are going to log would be the Log Deadband property.
At the same time, we configure what we want to log and define the directory where the *lgh / *idx files will be created daily. The *.lgh files contain the raw data and the *.idx files contain the indices for when we make a data request to retrieve them and speed up the queries. With this, we have answered where and how the data is logged; we can also say that they are stored in Wonderware's proprietary format. To date, apart from Wonderware products, there are, as far as I know, two applications that allow us to read these files without dependencies on Intouch. These are the LGH File Inspector and the Intouch Historical Data Exporter.
If we run the runtime again, we can already verify that the aforementioned files have been created for data storage.
And now let's see... Who logs? Who is responsible for saving and generating the files?
The answer is the viewer. The viewer is responsible for logging, by default it does so in Delta mode and according to the configuration that has been made for each tag.
In addition, there are a couple of parameters that we can add to the Intouch.INI regarding the Historicals to force the saving. They are as follows:
ForceLogCurrentValue = 1
ForceLogging = x (x = minutes 5 - 120)The next test was to close the Intouch Historical Data Server application, and it can be observed that data continues to be logged and the file sizes increase.
And we will encounter the error when we want to visualize the data in the Historical Trend Chart, we have no data, but... we are still logging.
After a restart, we see that we have all the data. NOTE: We cannot run the Intouch Historical Data Server application outside the scope of the viewer; it forces us to restart the viewer.
For the next... And to not extend this much more...
How can we verify that we are logging data? How to extract the stored data? Introduction to Histdata (Intouch Historical Data Access)