Backend

For each database into which data should be written or read from one backend must be defined. A backend is specific to a certain database type (e.g. InfluxDB®, PostgreSQL®, …). Several backends of the same type can be used (for writing / reading data into / from different database instances of the same DB type).

A backend for InfluxDB® and PostgreSQL® is already preinstalled and preconfigured. It is not recommended to change the values of the backend configuration (except for the username and the password of the database) unless you have detailed knowledge of the database and NGA.

Each backend configuration is saved in an internal data point called _NGA_B_<backend name> of data point type _NGA_Backend. A data point of this type exists for each backend. For detailed description, see the description of the panels below. The _NGA_Backend data point is described in the chapter Internal Data Points.

To change the values, open the Database Engineering panel via WinCC OA System Management > Database > Database Engineering
Note: Historical data is saved in different ways depending on the DB backend used. InfluxDB® stores the dpeName as text for each individual value change in the database. PostgreSQL® uses a relational database model with multiple entity tables.

For this reason, the reference ID of the DPE is saved in PostgreSQL® instead of the dpeName.

Figure 1. NGA backend overview panel

The Database Engineering panel consists of three panels: Backend, Profile and General.

  • The Backend panel is used to specify backend parameters related to buffering of data as well as general database data.
  • The Profile panel - see chapter Profile.
  • The General panel - see chapter General