Special FMS Command Notes

Requesting Event and Alarm Data in CygNet Measurement

When retrieving event and alarm data using the Request Missing Data command, it is possible to fail to retrieve data for devices whose timestamp does not correspond to the timestamp of the event or alarm. For best results, follow the recommendations below when retrieving event and alarm data.

Each event and alarm data group has a “now” timestamp of the device at the point when the request was made. However the timestamp is often not from the device, as many devices don't return a timestamp, so the UIS will use its current time and adjust it for the time zone of the device. This can cause data retrieval problems when the timestamp of the device doesn't match the time of the event or alarm.

For example, if you request data through “now” (current time) and the UIS reports that “now” in Device time is 5:01 p.m., the FMS will mark all events and alarms as received through 5:00 p.m. However, if the actual device thought it was 4:58 p.m. and then generated an event at 4:59 p.m., the Request Missing Data command would never retrieve that event because the next data request would start at 5:00 p.m.

Recommendations

The best way to avoid this situation is to do the following when retrieving event and alarm data.

• Always use the Request New Data command to retrieve event or alarm data.
• Don't request event or alarm data through “now.” Instead, always end the data request one hour prior to “now.”
• Schedule frequent configuration polls (with the Request New Data command) so the problem will be identified if events or alarms are missed.
• Make sure device timestamps don’t drift.