sys.dm_db_index_usage_stats (Transact-SQL)

THIS TOPIC APPLIES TO: yesSQL Server (starting with 2008)yesAzure SQL DatabaseyesAzure SQL Data Warehouse yesParallel Data Warehouse

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.

Note

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).

Note

To call this from Azure SQL Data Warehouse or Parallel Data Warehouse , use the name sys.dm_pdw_nodes_db_index_usage_stats.

Column name Data type Description
database_id smallint ID of the database on which the table or view is defined.
object_id int ID of the table or view on which the index is defined
index_id int ID of the index.
user_seeks bigint Number of seeks by user queries.
user_scans bigint Number of scans by user queries. This represents scans that did not use 'seek' predicate.
user_lookups bigint Number of bookmark lookups by user queries.
user_updates bigint Number of updates by user queries. This includes Insert, Delete and Updates representing number of operations done not the actual rows affected. For example, if you delete 1000 rows in one statement, this count will increment by 1
last_user_seek datetime Time of last user seek
last_user_scan datetime Time of last user scan.
last_user_lookup datetime Time of last user lookup.
last_user_update datetime Time of last user update.
system_seeks bigint Number of seeks by system queries.
system_scans bigint Number of scans by system queries.
system_lookups bigint Number of lookups by system queries.
system_updates bigint Number of updates by system queries.
last_system_seek datetime Time of last system seek.
last_system_scan datetime Time of last system scan.
last_system_lookup datetime Time of last system lookup.
last_system_update datetime Time of last system update.
pdw_node_id int Applies to: Azure SQL Data Warehouse, Parallel Data Warehouse

The identifier for the node that this distribution is on.

Remarks

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.

During upgrade to SQL Server 2008 R2 , SQL Server 2012 , or SQL Server 2014 , entries in sys.dm_db_index_usage_stats are removed. Beginning with SQL Server 2016 , entries are retained as they were prior to SQL Server 2008 R2 .

Permissions

On SQL Server , requires VIEW SERVER STATE permission.
On SQL Database Premium Tiers, requires the VIEW DATABASE STATE permission in the database. On SQL Database Standard and Basic Tiers, requires the Server admin or an Azure Active Directory admin account.

See Also

Index Related Dynamic Management Views and Functions (Transact-SQL)
sys.dm_db_index_physical_stats (Transact-SQL)
sys.dm_db_index_operational_stats (Transact-SQL)
sys.indexes (Transact-SQL)
sys.objects (Transact-SQL)
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