?yclical DPE archiving

[akim]

Hello everyone,

Tell me please, how to make a cyclical archiving of dpe, but not by DPE changing?

[leoknipp]

In WinCC OA values are only saved when they are changed. There is no functionality available which saves values in a defiined interval without any changes. This is normally not needed to save values in defined intervals in WinCC OA.

Why do you want to save the same value in a defined interval?

Best Regards
Leopold Knipp
Senior Support Specialist

[adaneau]

Hi,

Archiving in WinCC OA is event oriented so basically you need a change in data to archive (can be value, timestamp, quality,...)

For achieving cyclic archiving, I see 2 ways that I used in some projects in the past:

- Using dpFct statistical to generate every xxx period a data from a source (there I either use start or end value).
- Using a smoothing in the archive to block any news data for a period XXX-1s and having a polling without low level comparison on 1sec refresh. In this case I have no need to create additionnal DP but have a risk to not have exactly the same period all the time. I can also not have too small period ( I used it for 10min values). This also increase events on the system as I dont use low level.

Maybe someone is having better solution but from my side I have no other idea.

BR
Alex

[leoknipp]

Before implementing a work around you have to think about the use case.
There must be a good reason why the value needs to be saved every time.
For the common use cases, e.g. displaying data in the trend, there is no need to have the same value several times in the archive.

Best Regards
Leopold Knipp
Senior Support Specialist

[akim]

I use the first method that Alexandre Daneay described. You can also use the timedFumc() function.
But I thought that there is some standard solution.

The task: It is necessary to make a two-hour report.

In the attached picture you can see the result of my solution. It works with the existing archiving method(by value changing).
But the reason why I need cyclic archiving is simple: the customer wants to save the principle, as in the classical WinCC that is used by them now.

Thank you all

[leoknipp]

Please keep in mind that saving the same value all the time will
-- need more disk space
-- increase the times to read historical data as more data needs to be read and transferred
-- probably cause longer displaying time for data, e.g. in a trend as more data needs to be processed

The solution provided by Alexandre will possibly cause a higher load in the Event Manager, depending on the amount of dp elements which needs to be calculated.

If you use a timedFunc() you have to implement CTRL code which saves the correct values for the given, which will cause additional load for the system.

P.S.: There is no need for a standard solution as WinCC OA does not need data saved all the time without changes to fulfill reporting requirements.

Best Regards
Leopold Knipp
Senior Support Specialist

[akim]

I completely agree. But it doesn't matter to me that the OS will be overloaded, because I have a two hour report. I need a report in the form of:
00:00:00
02:00:00
04:00:00
06:00:00
...

The standard tool AES does not give me this opportunity. Since the value is archives by changing the time stamp and the time stamp can be changed when the quality of the dpe becomes bad or, on the contrary, good. Thus, the report becomes:
00:00:00
00:43:23
00:41:30
02:00:00
04:00:00
06:00:00
...

How can I display the data in the form I need in standard ways?

[frankySie]

(by Leopold Knipp) >>>Before implementing a work around you have to think about the use case.

exactly we had a usecase at one of our customers. Let me describe it to give you an understanding why such a feature is required sometimes.

At the customer some devices produce data in a very, very, .... very slow rate. For 6 month - 1 year just one new data was incoming from the machine. We, as developer, like this because it helps to save storage-space and the system load is really less.
But the customer is not happy. He has to provide actual data periodically to the government because the data has to fullfill legal regulations. A typical time frame for government's data-transmission is a month. Even if a data has not changed for a year, the customer need to have updated, actual data (+timestamp) in the database of Wincc OA.
It was a long discussion process with the customer to explain the data concept of Wincc OA. He has not accepted it.
We implemented the solution with the smooth config. It is described above by Alexandre Daneau.