Distributed alarm system data storage

There are several forms of data storage used in the Distributed Alarm system:

• Internal alarm memory (buffer)

  Most information about current and recent alarms is held in memory on various computer nodes. InTouch uses two memory locations: one for summary alarms (current) and one for historical alarms and events. This model is also used in the Distributed Alarm system.

  The memory for summary alarms grows as needed to accommodate all current alarms up to the limit of available memory. The memory for historical alarms can grow only to a pre-determined limit. After the historical memory reaches this limit, the oldest alarm records are discarded as new ones are added. In a multi-node environment, the alarm memory on the various nodes constitute a single collective of alarm memory.

  For information about setting the limit, see Configure the alarm buffer size.

• Alarm database

  The Alarm DB Logger creates a database, keeping track of when an alarm occurs, makes a sub-state transition, is acknowledged, and when it returns to normal. Essentially, these records constitute a history of alarms in the system.

Because it is based on the use of queries, the Distributed Alarm system supports using one computer node to log alarms for several other nodes.