Monitors for a large change in value of database free space over a set number of sample periods. A rapid large change in value could indicate a problem.
Unhealthy state is caused by a large change in free space over a set number of sample periods. This can be caused by:
A large autogrowthth setting for a file set to autogrowth.
A fast growing file that consumed a large amount of free space within a short period.
A foreign object or file consumed a large amount of free space hosted on the same disk as this file
Use the following link to view the performance data: Database Performance Data
This monitor aggregates the space available for each file within a Filegroup depending on each file configuration:
For a file that has no autogrowth, free space would be the difference between the initial size for a file and the used space.
In addition to the difference between the file size and the used space, the free space for files with autogrowth enabled would be the minimum of either the difference between the max size and the file size and the free space left on disk.
The free space calculations also take into account that the file can also fail to grow if the growth amount of the file is greater than the amount left on disk, and that the file cannot grow if the difference between the max size and the current file size is less than the growth amount. In these situations, available free space left on disk is not included as a part of the free space, because we cannot grow any longer.
This issue may be resolved by either:
Decreasing the growth amount for files with autogrowth
Modifying the thresholds for this monitor to suit the workload
Alternatively, if space percentage change is not a concern for the database:
Disable this monitor for this specific database or all databases