Monitors the space available on the log files and on the media hosting the log files. The space available on the media hosting the log files is only included as part of the space available if auto grow is enabled for one of the files and the “Include Disk Space” setting for the file group object is set to TRUE.
An unhealthy state is caused by having low available space across all log files. Low available space can be caused by:
Inadequate file configuration settings (size, max size, auto grow, etc.)
Inadequate space left on media
Lack of periodic regular backups
Log not truncating
The “Include Disk Space” setting for this monitor is set to FALSE for workloads that expect their files to grow.
Use the following link to view the performance data:
Database Performance Data
This monitor aggregates the space available for each log file within a database depending on each file’s configuration:
No Auto Grow
For a file that has no auto grow, available space would be the difference between the initial size for a file and the used space.
Auto Grow Enabled
In addition to the difference between the file size and the used space, the available space for files with auto grow enabled would be the minimum of either the difference between the max size and the file size and the free space left on disk.
Low available space for database log files that have auto grow could mean that the file is approaching the limits of the hosting logical drive. For files with auto grow enabled with a max size, low available space could also mean that the file is approaching the max size specified for a file.
The available 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 part of the available space because we cannot grow any longer.
This issue may be resolved by either:
Increasing the allocated size for log files if auto grow is disabled
Increasing the max size value for a log file if auto grow is enabled
Enabling auto grow for at least one file
Moving log files to another drive with more free space if growth space is limited
Performing regular backups of log files for FULL and BULK-LOGGED recovery modes
Investigate why log is not getting truncated:
Long open running active transactions
Long running backup operations
Replicated transaction open for a long time (Transactional Replication)
Mirror lagging behind principal server (Database Mirroring)
Set the “Include Disk Space” setting for this monitor to TRUE for workloads that expect their files to grow.
Modifying the thresholds for this monitor to suit the workload
Alternatively if log file available space is not a concern for the database:
Disable this monitor for this specific database or all databases
See SQL Server Books Online: Files and Filegroups Architecture