On a ClearSCADA system, you configure the ClearSCADA database so that entries in the database reference the devices and plant that you are trying to monitor on your system. This section summarizes the database items that you need to configure in order to read and write to data on other servers, using the DDE protocol.
To communicate with other servers using the DDE protocol, the DDE Driver has to be installed and running on the ClearSCADA servers on your system. The driver is represented by the DDE Client component in the ClearSCADA Installation Wizard’s Setup window. The component is located within the Server branch of the tree that is displayed in the window (see Install a Driver in ClearSCADA in the ClearSCADA Guide to Drivers).
When you configure DDE items in the ClearSCADA database, many of the settings for those items need to correspond to the settings on the relevant DDE servers on your system. You need to have access to, or a list of, these settings before you can configure the DDE database items successfully.
For instance, you need to know the read and write mechanisms that are supported by the DDE servers on your system, and the user names and passwords that allow the required level of access to the data if the DDE servers run on different machines to the ClearSCADA database. You also need to be familiar with DDE Components and Terminology.
You also need to be aware of which optional features are required for each DDE item. These features include:
- Alarm views
- Alarm redirections
- Historic data storage
- User methods.
You can also use core ClearSCADA features with DDE database items, including Lists, Actions, and Mimics. See the core documentation for details.
For each DDE device, you need to configure:
- DDE Servers to specify the servers on which data is to be scanned, along with any access and security properties required to communicate with those servers.
You need to configure one DDE Server item in the database for each server with which you want to communicate using the DDE protocol (see Configuring a DDE Server).
- DDE Scanners to specify which nodes are to be scanned and the rates at which the data is to be retrieved.
You need to configure a minimum of one DDE Scanner per DDE Server. You can attach multiple scanners to the same server. For instance, you might configure different scanner to have different scan rates or offsets, in order to retrieve some data at different intervals or times to other data.
For more information, see Configuring a DDE Scanner.
- DDE Points to represent the measuring instruments and control devices on the servers that are communicating using the DDE protocol.
For more information, see Points Used on DDE Scanners.
To minimize the time that it takes to configure the required DDE items, you may want to configure them in the order listed above, as the Scanner configuration requires that you specify a server, and point configuration requires that you specify a scanner, and so on.