This shows that the logical disk is filling up or is full.
To rectify this:
It is recommended that a backup of the system is taken before any files are moved or deleted.
Note: This problem can be raised by the Disks - Percentage Used alarm where thresholds are set on the percentage of disk space used, or the Disks - Free Space alarm where thresholds are set on available megabytes free. By default the Disks - Percentage Used alarm is enabled and the Disks - Free Space alarm is disabled.