SQL Server Wait Type: LCK_M_SCH_M

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a “wait” and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.

The LCK_M_SCH_M wait type in SQL Server is a type of wait that occurs when a task is waiting to acquire a schema modification lock. In SQL Server, a schema modification lock is a type of lock that is used to protect the structure of an object, such as a table or index, during certain operations. For example, a schema modification lock might be taken when a query is modifying the structure of an object, or when an index is being created. When a task is in the LCK_M_SCH_M wait state, it is waiting for the schema modification lock to be released before it can continue execution. This wait type is typically only seen when certain operations are being performed on an object in the database.

More details avilable on this wait type here: http://DatabaseHealth.com/Waits/LCK_M_SCH_M.html

Do you have a favorite tool for monitoring your wait statistics on SQL Server over time? This is something that you can use Database Health monitor to do. More details at http://DatabaseHealth.com.

If you are having performance issues assocaited with this wait type and need soem help, please contact us with our 30 minute consulation link.