Applies To: SQL Server 2014, SQL Server 2016 Preview
Returns counts of different types of index operations and the time each type of operation was last performed in SQL Server.
In Azure SQL Database, dynamic management views cannot expose information that would impact database containment or expose information about other databases the user has access to. To avoid exposing this information, every row that contains data that doesn’t belong to the connected tenant is filtered out.
sys.dm_db_index_usage_stats does not return information about memory-optimized indexes. For information about memory-optimized index use, see sys.dm_db_xtp_index_stats (Transact-SQL).
Applies to: SQL Server (SQL Server 2008 through current version), Azure SQL Database, Azure SQL Data Warehouse Public Preview.
To call this from SQL Data Warehouse, use the name sys.dm_pdw_nodes_db_index_usage_stats.
ID of the database on which the table or view is defined.
ID of the table or view on which the index is defined
ID of the index.
Number of seeks by user queries.
Number of scans by user queries.
Number of bookmark lookups by user queries.
Number of updates by user queries.
Time of last user seek
Time of last user scan.
Time of last user lookup.
Time of last user update.
Number of seeks by system queries.
Number of scans by system queries.
Number of lookups by system queries.
Number of updates by system queries.
Time of last system seek.
Time of last system scan.
Time of last system lookup.
Time of last system update.
Every individual seek, scan, lookup, or update on the specified index by one query execution is counted as a use of that index and increments the corresponding counter in this view. Information is reported both for operations caused by user-submitted queries, and for operations caused by internally generated queries, such as scans for gathering statistics.
The user_updates counter indicates the level of maintenance on the index caused by insert, update, or delete operations on the underlying table or view. You can use this view to determine which indexes are used only lightly by your applications. You can also use the view to determine which indexes are incurring maintenance overhead. You may want to consider dropping indexes that incur maintenance overhead, but are not used for queries, or are only infrequently used for queries.
The counters are initialized to empty whenever the SQL Server (MSSQLSERVER) service is started. In addition, whenever a database is detached or is shut down (for example, because AUTO_CLOSE is set to ON), all rows associated with the database are removed.
When an index is used, a row is added to sys.dm_db_index_usage_stats if a row does not already exist for the index. When the row is added, its counters are initially set to zero.
Requires VIEW SERVER STATE permission. For more information, see Dynamic Management Views and Functions (Transact-SQL).