For real-time and average trending, how is data stored in the database when the parameter's value does not change for a period of time. It appears that for real-time trended parameters, entries are only added to the dbase table when the value changes, but for average trended points I have seen this same behavior at times but also entries at 5 min intervals at other times. Trying to understand this behavior so I can in turn understand the response from various Webservices API calls.
For real time trending it is indeed the case that when a value changes it gets written to the database.
For average trending a point is written to the database when:
- During the window a value change happened (1)
- During the previous window a value change happened (2)
This means that if a value changes at 12:48 the following points will be written to database
- RT: time:12:48
- AVG: time:12:50 (For case (1))
- AVG: time: 12:55 (For case(2))