The following list provides terms and definitions specific to historian
terminology:
- active historical data set
- Holds the most recent historical data captured for all configured
history tags. The data set holds the contiguous historical data record from the
time it was created until the present.
- archives
- Files used to store historical data. Each archive file contains
events for a time period specified by the archive start time and end time.
- current historical data set
- Data set created by rollover of the active historical data set. A
current historical data set is a former active historical data set that has
been completed by hitting the time or size limit rules or by direct creation of
a new active data set. A current historical data set holds historical data for
a collection of history tags within the time span of the data set. One or more
current historical data sets may exist in Primary storage.
- extended historical data set
- A historical data set that has been placed back online through the
use of the Continuous Historian Administration application. Such data sets may
be for any history tags for any period of time, without continuity with the
active and current historical data sets.
- Primary storage
- A storage area on each workstation with a historical data server
installed. This area holds a collection of historical data sets, including one
active historical data set, zero or more current data sets, and zero or more
extended historical data sets.