iSMA-B-MAC36NL User Manual
Version 1.4
www.gc5.pl
Page 36 / 51
Note: NV-RAM does not preserve data or files external to the station.
Please note that if iSMA-B-MAC36NL power event occurs when station users have unsaved
file changes, say in a Px file or Nav file being edited, those unsaved changes are lost.
Station users may be aware of such an event and react by saving changes (click the Save
button in the active view).
Providing that communications are still established, the file edited may be saved. Or, power
may be lost only momentarily, and then remain stable until the user does a normal save.
Note: iSMA-B-MAC36NL does not provide a similar save opportunity after a power bump
—
it
is already busy rebooting. Therefore, as a best practice, you should advise system users of
iSMA-B-MAC36NLs to save often when editing items like Px graphics and Nav files.
The Data Recovery Service writes current values as they occur to a block of NV-RAM. When a
block is full, the service copies it from NV-
RAM to the controller’s flash memory. A station that
creates rapid COV (change of value) histories may fill the NV-RAM data blocks too frequently,
triggering a database save possibly every couple of minutes. Ideally, such database saves to
flash memory should occur no more than once an hour.
Saving the database too frequently results in inefficient use of controller CPU time and
potential flash problems.
Flash memory is designed to be written to a certain number of times. Several variables
contribute to how often the database needs to be saved, including:
•
Rate of changes that need to be persisted
•
Size of the changes (histories, alarms, and setpoint changes differ in size)
•
Amount of free flash memory space