Blocking

Expand the “Blocking” row to view a chart that shows the number of blocking events for each database.

Blocking events are raised by SQL Server when a session waits on a lock longer than the blocked process threshold. By default the threshold is 0 (no events). The QMonitor setup script sets the threshold to 10 seconds as a recommended starting point. If you see too many events, increase the threshold. After you’ve resolved most blocking events, you can experiment with lowering the threshold.

Under the chart is a list of blocking events with columns for time, sequence, database, object ID, duration, lock mode, and resource owner type. Use the column filters and sort controls to filter and sort the table.

Click a row to open the Blocking detail dashboard.

The top table in the detail view shows the same event information as the events dashboard. The Blocking XML panel displays the blocked process report in XML format. That report contains many nodes; documenting every node is beyond the scope of this documentation.

The XML includes one or more nodes and one or more nodes. These nodes identify the blocked and blocking processes and provide details about the resources the blocked process was waiting on.

The bottom grid lists sessions that were running around the event time, giving a quick overview of blocking and blocked processes. Use the buttons above the grid to set the time window around the event from 1 to 15 minutes.