Accessing WinCC OA data

Manager

Communication and data exchange between any OPC clients and the WinCC OA OPC server using WinCC OA is performed by the manager WCCOAopcsrv, which establishes communication with the Event Manager. The manager must be added to the manager list, and the process started via the console:

WCCOAopcsrv

When starting the WinCC OA OPC client (WCCOAopc) in the console, the WinCC OA OPC server is started automatically in the background.

Address space

The server address space contains the data which the WinCC OA OPC server provides for clients. The data to create the address space can be defined either via

• data point groups (refer to OPC DA data point groups) or

• CNS (refer to OPC DA server CNS)

Subscribe on use

By default, the server subscribes to OPC items with a dpConnect as soon as an item is added to the address space.

The config entry subscribeOnUse = 1 specifies that the OPC server only subscribes to data point elements if the corresponding OPC item is requested by a client. This mode shall only be enabled if the address space is very big and the clients always need only a part of the items.