ClearSCADA provides the facilities to retain historical data online and to archive historical data. ClearSCADA can generate the following types of historic data:
- Events—These are a record of the activity on your system. ClearSCADA stores events in the Event Journal. Event Journal data is stored on disk for a specified duration and is then deleted.
- Configuration Changes—Historic data relating to changes made to the configuration of your system. For example, if an engineer changes the configuration of a point in the database, a record of that alteration is created and stored as a 'configuration change'. This is an optional facility and is disabled by default.
- Historic Data—Historic data relating to reported values, modified values, annotated values and suppressed values for database items that support historic data storage (database points, master station accumulators and some driver-specific items). There are four categories of Historic Data:
- Raw—Historic data that has been received for points in the database.
- Modified—Historic data that has been altered by ClearSCADA users.
- Annotation—Annotations that have been inserted by ClearSCADA users.
- Suppression—Historic data that relates to suppressed alarms. A historic record is created whenever alarms are suppressed on a point (and also when alarms stop being suppressed on a point).
- Alarm Summary—This provides you with a summary of alarms that have occurred on your system. This includes when alarms occur, alarm change state or whether alarms are acknowledged .This is an optional facility and is disabled by default.
Historic data is generally retained online for a specified duration, after this period of time expires the data is deleted to allow space for new data. Modified historical data is retained online permanently when historic data enabled. To retain historic data permanently it can be Archiving.
Archives are used to:
- Provide long-term offline storage of alarm summary, historic data, event and configuration changes messages.
- Allow multiple backup copies of data to be stored externally. For example, CD-Rs and DVDs can be stored in a fire safe.