Users can force a redundancy failover for FrameWorX or individual Point Managers. Point Managers and FrameWorX as a whole can have a particular point associated with them, called an enabling point, and when the enabling point evaluates to zero or bad quality that FrameWorX or Point Manager instance will go offline.
Note: Bad – Invalid Point Name is an exception to this rule. It is the only "bad quality" that will not cause FrameWorX or the point manager to go offline. This is to prevent cases where someone accidentally types in a point name that doesn't exist.
This feature can be used to identify Point Managers or FrameWorX instances that are in an undesirable state and prevent clients from using them.
In a standard redundancy scenario, a client will only connect to the secondary Point Manager if the primary Point Manager is not responding. There could be other problems with the primary Point Manager, however, such as if it has lost connection to its source data. The primary Point Manager would still be detected as online in this case, even though all of its data points would be bad quality. Clients may continue talking to it, even if the secondary Point Manager has good quality points. With this enabling point feature, the presence of a particular bad quality point could be used to force this Point Manager to report itself as offline, causing clients to failover to the second functional Point Manager.
To configure an enabling point for FrameWorX, open Platform Services Configuration from the Workbench or the Start menu, then go to the Advanced tab. Enter a point name into the Server Enabling Point field.
To configure an enabling point for an individual Point Manager, open Platform Services Configuration from the Workbench or the Start menu, then go to the Point Managers tab. Find your desired Point Manager in the list, then scroll to the right to find the Enabling Point column. Enter a or point name into this column. Note that this feature is only supported for Point Managers running out-of-process.
Enabling points must be a single point, not an expression, however users can configure an expression tag in the Unified Data Manager (Platform Services > Unified Data Manager > Expressions) and use that exp: tag as an enabling point, if desired.
Note that FrameWorX and Point Managers disabled by their enabling point will still function, they will simply close any existing client connections and reject any further communication attempts from clients until the enabling point allows them to come online again.
These features were designed for a redundancy scenario, but they can also be used in a non-redundant scenario to temporarily prevent clients from connecting to a particular Point Manager or FrameWorX.
Users are encouraged to utilize this feature with care, as using an unreliable enabling point can cause a FrameWorX server or Point Manager to appear to go offline for no good reason. If a FrameWorX server or Point Manager's communication was disabled due to its enabling point, a message will be logged in TraceWorX at the error level.
Note: The exact wording of this message is:
Server execution disabled due to value of: serverEnabledPoint.PointName
This feature is similar to the preexisting "Controlled Redundant Servers" feature for OPC Classic servers, configured in the Workbench under Platform Services > FrameWorX > Server Settings > GenBroker64 Settings. Note that the "Controlled Redundant Servers" feature is evaluated on the client side, which is different from the enabling points for FrameWorX and Point Managers.
See Also: