There are essentially three steps in the “history logging” life cycle, as shown in Figure 163:
-
collect
involves defining the parameters that specify what data will be recorded and when (or how often) it will be recorded. For example, you can collect data whenever a change of value occurs - or at a regular time interval that you specify.
To collect history information you need to:
-
Add history extensions to a component (refer to Add history extensions to a component)
-
Configure the extensions (refer to Configure history extensions)
-
Use a valid history name (part of configuration, see, About history names)
Refer to Add history extensions to a component for more details.
-
-
store
involves defining the parameters of the history database file. For example, you can customize the name of the database file, define the maximum number of records to save, and choose metadata to add to the records. Refer to Configure history extensions for more details.
-
archive (transfer)
includes importing and exporting records from one station to another station. For example, you can limit your local station records to a small number that you specify and archive all records to another station. Refer to Archiving for more details.
You can add extensions to a component’s property sheet in order to extend the functionality of the component. By adding a history extension, the real-time value or status of the component’s output can be collected as a time-stamped entry in the associated history table. History extensions are available in the history palette, as shown in Figure 164. The history table is not stored as part of the component’s data but is a separate collection of data simply referred to as the history.
