The Scan attribute has the default value of 1, indicating that the Interface should collect data for the point. Setting the Scan attribute to 0 turns data collection off. If the Scan attribute is 0 when the interface starts, the Interface writes SCAN OFF to the point. If the user changes the Scan attribute from 1 to 0 while the interface is running, the Interface also writes SCAN OFF.
There is one other situation, which is independent of the Scan attribute, where PI Ping will write SCAN OFF to an interface point. If a point that is currently loaded by the Interface is edited so that the point is no longer valid for the Interface, PI Ping removes the point from service, and writes SCAN OFF to the point. For example, if a user changes the PointSource of a point that is currently loaded by PI Ping, the Interface will no longer service the point and write SCAN OFF to it.
The Shutdown attribute is 1 (true) by default. The default behavior of the PI Shutdown subsystem is to write the SHUTDOWN digital state to all PI points when PI starts. The timestamp that is used for the SHUTDOWN events is retrieved from a file that is updated by the Snapshot Subsystem. The timestamp is usually updated every 15 minutes, which means that the timestamp for the SHUTDOWN events will be accurate to within 15 minutes in the event of a power failure. For additional information on shutdown events, refer to the PI Server manuals.
Note: The SHUTDOWN events that the PI Shutdown subsystem writes are independent of the SHUTDOWN events that the Interface writes when the user specfies the stopstat=Shutdown command-line parameter.
SHUTDOWN events can be disabled from being written to PI when PI restarts by setting the Shutdown attribute to 0 for each point. Alternatively, the default behavior of the PI Shutdown Subsystem can be changed to write SHUTDOWN events only for PI points that have their Shutdown attribute set to 0. To change the default behavior, edit the \PI\dat\Shutdown.dat file, as discussed in PI Server manuals.