The FreDisk parameter shows the amount of free space (in megabytes) on the drive of the selected workstation where the DeltaV \DVData directory is installed. For controllers, the value of this parameter is always 0.
To avoid problems with the database, it is recommended that you create an alarm to notify you when the disk space on the ProfessionalPLUS workstation drops below a certain level. A sample module, MONITOR_FREEDISK, is included in \DeltaV\Samples and can be used as a starting point to create the alarm.