Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 68)

Interface Disconnected Startup
62
Validation
CAUTION: Users must not modify the caching files created by the interface. User
modification of either of the caching files has the potential of invalidating the file
and inducing a data loss situation.
If a file has been modified by the user, it should be deleted to allow the interface to
create valid files necessary for the Disconnected Startup configuration. Newly
created files will require a connection to the Historian Server to start the interface.
An interface starting in the disconnected startup configuration requires the caching files be
validated to determine their usability. The validation process ensures the point and digital set
cache files are designated for a particular instance of the interface and the files are capable of
receiving new data. If the cache files are validated, the process will then provide the interface
with the stored Historian Server versioning information necessary to start the interface.
Finally, the validation process determines if the cache file has stored all point information
needed to start the interface without a connection to the Historian Server. If the validation
process determines the cache file is not complete, the interface will wait for a connection to
the Historian Server to become available. The Historian Server connection is needed to finish
initializing the necessary cache files. The status of the validation process is logged in the
pipc.log file.
A file which cannot be validated will be renamed and a new file will be created as described
in the ―Creation‖ section. Renamed files will contain an inserted numerical date-time change
string in the filename. If either of the point or digital set cache files cannot be found, the
necessary file(s) will be created as previously described. The ―Messages‖ section of this
document contains a listing of typical messages, which includes the renaming of an invalid
file, sent to the pipc.log file during the validation mode.
Construction
Note: If one or both of the cache files becomes invalid at any time during the construction
process, the interface will disable the disconnected startup feature and continue to
operate in the normal operation profile. During normal operation, a connection to
the Historian Server is required for the interface to start.
This construction mode of operation is where the cache files are populated with the
necessary digital state and point attribute data.
Construction of the digital cache file is determined as follows. If the interface requires
caching of the system digital state set, then all the system digital states will be retrieved from
the Historian Server and stored in the digital cache file. If the interface receives a digital
point from the Historian Server or queries the server for a digital point, all the digital states
for the digital set associated with the Historian point will be cached. Multiple points with the
same digital state set will only require the complete digital set to be cached once.