An uninterruptible power supply (UPS) is designed to provide emergency power in case of a power failure. This can be helpful by providing enough time for the system to shut down properly after loss of power. If the UPS is able to communicate with the computer's operating system, it can signal a shutdown in this event. The operating system can begin closing applications in an orderly manner while powered by the UPS.
The operating system will typically flush is own cache to disk during shutdown. It may not cause the disk controller to flush its cache.
If the UPS signals a shutdown, and FairCom DB is properly configured, it should cleanly shut down in this situation. The UPS must be properly configured to safely shut down the computer and FairCom DB Server before the UPS battery fails.