Rockwell Automation FactoryTalk Historian SE 3.0 H2H Interface User Guide - Manual (Page 17)

FactoryTalk Historian To Historian Interface User Guide 11
Chapter 2.
Principles of Operation
The FactoryTalk Historian to Historian interface copies tag data from one Historian Server to
another. It consists of a single executable and startup configuration file. No specific tag limit
exists for the interface. However, data throughput (events/second) can be limited by network
quality and/or system resources on the source and receiving Historian Servers. Users can
configure the interface to copy exception (snapshot) or archive data. Although it is possible
for one copy of the interface to do both, it is highly recommended that separate copies are
used for this purpose to ensure a high level of performance.
Interface Startup
On startup, the interface reads its configuration file for site-specific operating parameters.
This file contains required and optional configuration information, such as source and
receiving Historian Server, data update rates, and history recovery settings. Next the interface
establishes a connection to each Historian Server and initializes its tag lists.
Each client connection to a Historian Server is associated with a specific PI user. This PI user
determines what permissions are granted to the client. The source Historian Server must grant
the interface permission to read tag attributes and data for interface source tags. On the
receiving Historian Server the interface requires read access for tag attributes and read and
write data access for its tag list. See the section
Tag and Node Security for additional
information.
As the interface initializes its tag lists, tags are grouped internally by scan class assignment.
Each interface tag must be configured for a unique source tag. If an invalid tag configuration
is detected, the tag is either rejected or added to the tag list and marked in error. In either case
a message will be logged with specific information about the error. The interface outputs
messages to
pipc.log , which can be found in the local \pipc\dat directory.
After the interface is finished building its tag lists it calculates the time offset between
Historian Servers. The offset is updated every 2 minutes and used for data timestamp
adjustments, if configured, and to timestamp interface status events. It is required that each
participating node has the correct system time for its configured time zone. At this point the
interface is ready to begin data collection.