Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 58)

Interface Disconnected Startup
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enabled. Once satisfied with interface operation and data collection, enable disconnected
startup as described in this document and restart the interface.
Limitations
The following section describes the known limitations imposed on an interface running in the
disconnected startup configuration.
Extended Attribute Lengths
To maximize the functionality of the disconnected startup configuration, the use of a
Historian Server version 2 or later is recommended. The use of Historian Server version 2 or
later in conjunction with PI API version 1.6.1.x or later provides greater field lengths for the
tag, descriptor, exdesc, instrumenttag, and pointsource attributes.
Moreover, the PI SDK is no longer required for support of the increased field lengths. The
following table lists the maximum field lengths for a given Historian Point attribute for the
version of Historian Server used. In all cases, the PI API version is assumed to be 1.6.1.x or
later to support disconnected startup.
Attribute Maximum Length
(PI API 1.6.1.x or later on Interface Node)
Attribute Historian Server
2.x or higher
Historian Server
Below 2.x
Tag 1023 255
Descriptor 1023 26
ExDesc 1023 80
InstrumentTag 1023 32
PointSource 1023 1
Note: If the actual data stored for the point attribute is greater than the maximum
field length specified in the table, the returned value for the attribute will be
truncated to the maximum length for the given Historian Server version.
Interfaces Using the PI SDK
Interfaces utilizing the Historian SDK may or may not support disconnected startup. Some
interfaces by default create a Historian SDK connection to retrieve data from the Historian
Server. The operational need for the Historian SDK is interface specific. For example, the PI
SDK might be used to create Historian Points, collect information from components such as
the Module Data Base (MDB), and/or retrieve extended point attribute information. Use of
the PI SDK by the interface to retrieve the extended attribute information from the host
Historian Server is not supported. The disconnected startup feature utilizes the PI API to
retrieve extended point information from the Historian Server that is stored in the necessary
caching files. Interfaces supporting disconnected startup will explicitly say that disconnected
startup is supported in the ―Supported Features‖ table of the interface manual.