The following distinction is made based on the refresh ID:
● Event packages with the refresh ID contain only historical events. These events can also
still be pending.
● Event packages without the refresh ID contain only newly generated events.
Note
An event package never contains historical and new events at the same time.
"advise" read mode
With the "advise" mode, archived messages are read starting at a defined time in the past.
After reading all archived messages, new messages are sent as with an active subscription.
The archived messages are transferred in chronological order related to each OS server. First
the archived messages starting at the start time are transferred. The new archived messages
are then transferred. An active subscription is used for the "advise" read mode. If you execute
the "SetFilter" function on an active subscription, the historical alarms are transferred
immediately. If you execute the "SetFilter" function on an inactive subscription, the archived
messages are transferred only after the subscription is activated.
If you want to use the "advise" read mode with an inactive subscription, follow the steps below:
1. SetFilter
2. Set the subscription to active with SetState
If you deactivate the subscription, the transfer is interrupted. If you set the subscription to
"inactive", the transfer is stopped. A "SetFilter" is discarded while the subscription is active. A
"Refresh" on an active "historical" subscription in "advise" mode works in exactly the same
way as a with a standard subscription:
All pending condition-related events are transferred in packets with the refresh ID. The last
packet also has the "Last Refresh" ID. In "advise" mode, a "refresh" call has no influence on
the reading of historical alarms.
Note
Note that you must not specify an end time with "advise".
6.6.6 Identifying archived messages
Principle
Archived messages are distinguished by an additional flag in the EventType.
This flag is connected with the real EventType via an OR link:
OpenPCS 7 interface
6.6 OPC Historical Alarms and Events (OPC "H" A&E)
OpenPCS 7
Function Manual, 05/2012, A5E02780178-02 79
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