Milestone M50 - Manual (Page 194)

Milestone Husky M30/M50 Administrator's Manual
www.milestonesys.com 194 Misc concepts and tasks
Misc concepts and tasks
About daylight saving time
Daylight saving time (DST, also known as summer time) is the practice of advancing clocks in order
for evenings to have more daylight and mornings to have less. Typically, you move clocks forward one
hour during the spring season and adjust them backward during the fall season. Note that use of DST
varies between countries/regions.
When you work with a surveillance system, which is inherently time-sensitive, it is important that you
know how the system handles DST.
Spring: Switch from Standard Time to DST
The change from standard time to DST is not much of an issue since you jump one hour forward.
Typically, the clock jumps forward from 02:00 standard time to 03:00 DST, and the day has 23 hours.
In that case, there is no data between 02:00 and 03:00 in the morning since that hour, for that day, did
not exist.
Fall: Switch from DST to Standard Time
When you switch from DST to standard time in the fall, you jump one hour back. Typically, the clock
jumps backward from 02:00 DST to 01:00 standard time, repeating that hour, and the day has 25
hours. In that case, you reach 01:59:59, then immediately revert back to 01:00:00. If the system did
not react, it would essentially re-record that hour, so the first instance of, for example, 01:30 would be
overwritten by the second instance of 01:30.
Because of this, Milestone Husky product forcefully archives the current video in the event that the
system time changes by more than five minutes. The first instance of the 01:00 hour is not viewable
directly from clients. However, the data is recorded and safe, and it can be browsed using the XProtect
Smart Client by opening the archived database directly.
About protecting recording databases from corruption
You can select which action to take if a camera database becomes corrupted. The actions include
several database repair options. While it is good to have such options, Milestone recommends that
you take steps to ensure that your camera databases do not become corrupted.
Power outages: use a UPS
The single-most common reason for corrupt databases is the recording server being shut down
abruptly, without files being saved and without the operating system being closed down properly. This
may happen due to power outages, due to somebody accidentally pulling out the server's power cable,
or similar.
The best way of protecting your recording servers from being shut down abruptly is to equip each of
your recording servers with a UPS (Uninterruptible Power Supply).
The UPS works as a battery-driven secondary power source, providing the necessary power for
saving open files and safely powering down your system in the event of power irregularities. UPSs