You need to decide what exactly you want to control. For example.
1) If there is a data load schedule, you can use the ReloadTime() functions to show and control the time of the last actual load.
2) With the help of function ScriptError(), you can control the process of loading data in Qlik Sense if there are errors etc.
In either case, you need to define a specific list of causes / conditions under which the data in Qlik Sense can be considered irrelevant . After that, you can already look for specific ways of control.
Now that I'm using the ReloadTime() function, I've been able to detect that although I've scheduled an automatic reload for every 15 minutes, now it's 10:10 AM and I see the last reload took place at 9:34 AM.
Is there any reason for that? Does it mean I may have an issue in the reload script? I've noticed that I have variables that are not being updated (such us vCurrentDay=Today(), that keeps showing the date corresponding to two days ago).