The Snapshot Subsystem gets the new data from the Interface Node and holds the most recent
value for each point. This most recent value is called the Snapshot for that point.
When a new event comes in, it becomes the Snapshot for that point. The PI Server evaluates the previous Snapshot according to the compression specifications and either sends the new value to the Event Queue or discards it.
These values in the Snapshot Subsystem are called Snapshot events or, sometimes, just
Snapshots. The collection of all the Snapshot values for all the points is the Snapshot
database.
compression data