Rockwell Automation FactoryTalk Historian SE 3.0 H2H Interface User Guide - Manual (Page 51)

FactoryTalk Historian To Historian Interface User Guide 45
Scan
By default, the Scan attribute has a value of 1, which means that scanning is turned on for the
point. Setting the Scan attribute to 0 turns scanning off. If the Scan attribute is 0 when the
interface starts, a message is written to the
pipc.log and the tag is not loaded by the
interface. There is one exception to the previous statement.
If any Historian point is removed from the interface while the interface is running (including
setting the Scan attribute to 0), SCAN OFF will be written to the Historian point regardless of
the value of the Scan attribute. Two examples of actions that would remove a Historian point
from an interface are to change the point source or set the Scan attribute to 0. If an interface
specific attribute is changed that causes the tag to be rejected by the interface, SCAN OFF
will be written to the Historian point.
Shutdown
It is recommended that shutdown events are disabled for all interface tags. There are two
shutdown events; when the Historian Server is stopped and when the interface is stopped. The
Shutdown tag attribute is used to enable Historian Server shutdown events. See section
Interface Status Events for information regarding interface shutdown events.
Shutdown events are written to tags when the Historian Server is stopped to indicate data is
not being collected. In some cases when the Historian Server is not running it creates a gap in
data. However if interface history recovery is enabled a shutdown does not indicate a period
of lost data.
If a tag is configured for shutdown events one is written when the server is stopped then again
when it is started. Since the shutdown event on startup will be the current value for the
interface tag it is used as the starting for history recovery. This results in a data gap for the
Historian Server shutdown period.
Bufserv and PIBufss
It is undesirable to write shutdown events when buffering is being used. Bufserv and PIBufss
are utility programs that provide the capability to store and forward events to a Historian
Server, allowing continuous data collection when the Server is down for maintenance,
upgrades, backups, and unexpected failures. That is, when Historian is shutdown, Bufserv or
PIBufss will continue to collect data for the interface, making it undesirable to write
SHUTDOWN events to the Historian Points for this Interface. Disabling Shutdown is
recommended when sending data to a Highly Available Historian Server Collective. Refer to
the Bufserv or PIBufss manuals for additional information.
Exception and Compression
Interface data may or may not be subjected to exception and compression depending on
receiving Historian Server version and interface configuration. In either case it is
recommended users configure the interface and tag attributes to prevent compression from
causing data mismatches between Historian Servers.