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Use of the OPC Server Setup tag is restricted to VTScada installations that include this feature as part of the license key. You can confirm whether this feature is enabled by opening the About VTScada dialog from the VTScada Application Manager.
Server Name: Trihedral.VTSOPC.DA
The OPC Server Setup tag is used to turn your application into an OPC Server. Minimal VTScada configuration is required on your part to do this.
OPC security is handled by Windows via user and group security permissions set using the Microsoft Component Services dialog and the COM Security tag of the My Computer dialog. Please refer to Securing an OPC Server for more information on OPC security.
Only one OPC server may be defined per application. Attempting to define a second server in the same application will result in an error dialog stating "An application can have at most one OPC Server Setup tag".
Note: Use of the same name space for more than one application is strongly discouraged as it will cause significant problems.
There are no widgets for this tag. When the OPC Server Setup tag has been created, the application’s OPC-supporting tags become available on the VTScada OPC server.
OPC Classic Configuration - Technical information about the OPC Server configuration in VTScada.
The ID tab of every tag includes the same common elements: Name, Area, Description, and Help ID.
Uniquely identifies each tag in the application. If the tag is a child of another, the parent names will be displayed in a separate area before the name field.
You may right-click on the tag's name to add or remove a conditional start expression.
The area field is used to group similar tags together. By defining an area, you make it possible to:
- Filter for particular tag groups when searching in the tag browser
- Link dial-out alarm rosters to Alarm tags having a particular area
- Limit the number of tags loaded upon startup.
- Filter the alarm display to show only certain areas.
- Filter tag selection by area when building reports
When working with Parent-Child tag structures, the area property of all child tags will automatically match the configured area of a parent. Naturally, you can change any tag's area as required. In the case of a child tag, the field background will turn orange to indicate that you have applied an override.
To use the area field effectively, you might consider setting the same Area for each I/O driver and its related I/O tags to group all the tags representing the equipment processes installed at each I/O device. You might also consider naming the Area property for the physical location of the tag (i.e. a station or name of a landmark near the location of the I/O device). For serial port or Roster tags, you might configure the Area property according to the purpose of each tag, such as System or Communications.
You may define as many areas as you wish and you may leave the area blank for some tags (note that for Modem tags that are to be used with the Alarm Notification System, it is actually required that the area field be left blank).
To define a new area, type the name in the field. It will immediately be added. To use an existing area, use the drop-down list feature. Re-typing an existing area name is not recommended since a typo or misspelling will result in a second area being created.
There is no tool to remove an area name from VTScada since such a tool is unnecessary. An area definition will exist as long as any tag uses it and will stop existing when no tag uses it (following the next re-start).
Tag names tend to be brief. The description field provides a way to give each tag a human-friendly note describing its purpose. While not mandatory, the description is highly recommended.
Tag descriptions are displayed in the tag browser, in the list of tags to be selected for a report and also on-screen when the operator holds the pointer over the tag’s widget. For installations that use the Alarm Notification System, the description will be spoken when identifying the tag that caused the alarm.
The description field will store up to 65,500 characters, but this will exceed the practical limits of what can be displayed on-screen.
This note is relevant only to those with a multilingual user interface:
When editing any textual parameter (description, area, engineering units...) always work in the phrase editor. Any changes made directly to the textual parameter will result in a new phrase being created rather than the existing phrase being changed.
In a unilingual application this makes no difference, but in a multilingual application it is regarded as poor practice.
Help Search Key
Used only by those who have created their own CHM-format context sensitive help files to accompany their application.
An OPC Server has two configurable properties in addition to its ID information:
- The name space for this application on the Trihedral OPC Server. This is a required field.
- The Disallow Writes check box is there as a security feature. If selected, clients can query data from the server, but cannot write to it.
As a convenience, the server’s Prog ID will also be shown in this screen.
You may find it easiest to reuse the application's name for the server namespace. You should not use the same name space for two applications.