Garbage Collection State (rollup)

Summary

Note: This monitor is a dependency (rollup) monitor. The health state for this monitor is determined by best state of any member monitor. Please also review the knowledge base article for related unit monitors.

This monitor reports a Critical State and raises an alert if the Garbage Collector Fill Factor (an amount of space used by active rows in In-Memory data files, expressed as a percentage of the size of data files) drops below the Threshold setting for all related unit monitors.

Garbage Collection Fill Factor for Memory Optimized Data File Group is the metric that shows the average fill factor across all active data/delta files containing inserted/deleted rows. If this metric is lower than 50%, it indicates that automatic merge is falling behind. This is not an immediate cause of concern as long as the number of CFPs (checkpoint file pairs) is below 8000 and you have plenty of storage available In-Memory optimized file group.

More information can be found under the sys.dm_db_xtp_checkpoint_files (Transact-SQL) documentation

http://msdn.microsoft.com/library/dn133201%28v=sql.120%29.aspx

‘How Garbage Collection works’ section can be found under the topic 'Creating and Managing Storage for Memory-Optimized Objects'

http://msdn.microsoft.com/library/dn133174%28v=sql.120%29.aspx

Causes

Merge of CFP is kicked off based on an internal merge policy. Please refer to this article for details.

Resolutions

Perform a manual merge and force garbage collection as described in these articles:

• Monitoring and Troubleshooting Merge for Data and Delta File Pairs

• Forcing Garbage Collection On Merged Data Files

Overrideable Parameters