Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 70)

Interface Disconnected Startup
64

Retrieve event counter point configuration.

Retrieve system digital state set if requested.

Retrieve point configuration for points matching interface point source value. This
includes retrieving the digital state set for digital points.

Retrieve additional points required by interface. (Trigger, Source, etc.)
The interface will request point update information from the Historian Server at regular
intervals. The API Cache Manager will process updates received and modify the point cache
file if necessary to keep the cache files up to date. The update(s) will then be returned to the
interface for proper handling.
Synchronization
During interface disconnected startup with fully configured cache files, only the cache files
will be used to configure the interface with the necessary data to begin data collection. If the
interface has been disconnected from the Historian Server, the point configuration data
stored in the cache files may no longer match what is currently on the Historian Server. Point
attribute changes may have been made or points matching the interface point source may
have been added or deleted. Therefore, a synchronization mechanism is required to make
sure the Historian point configuration data running on the interface is up to date. The
synchronization mode keeps the caching files up to date and passes any changes in point
configuration to the interface for processing.
The synchronization process can only begin after the interface has been successfully started
using the disconnected startup configuration, entered its control loop, and established a
connection to the Historian Server. Once these conditions are satisfied, the UniInt Cache
Manager will request the API Cache Manager to retrieve a list a Historian Points matching
the interface point source from the Historian Server. If a point received from the Historian
Server does not exist in the point cache, it will be added to the cache and then a point create
update will be sent to the interface. If a point has been modified as indicated by the
―
changedate ‖ attribute, the cache will be updated with the correct attribute information and
a point edit update will be sent to the interface. A comparison of the points found on the
server is made to what currently exists in the caching files. If a point is found in the cache
file that no longer exists on the Historian Server, a point delete update will be sent to the
interface.
The optional /CacheSynch startup parameter, described in the Startup Command File
Configuration section, specifies whether cache synchronization is enabled and the time
period allocated to synchronization. By default, synchronization of the cache files is enabled
and the time period allocated for synchronizing the cache is set to a default of 250
milliseconds (ms) per synchronization attempt. This means one iteration through the
interface control loop can use a maximum of 250ms to synchronize as many points as it can.
The synchronization process will continue in this manner until all the points have been
synchronized. Once the cache files have been synchronized, cache synching will be disabled
unless there is an interruption with the connection with the Historian Server. If the Historian