Blocking occurs when one session holds a lock on a specific resource. The same session or additional sessions attempt to acquire a conflicting lock type on the same resource.
The Overview screen displays a graph of the number of Blocking Events that occurred over the chosen time range by default, in the top pane of the screen, with another option to display the total number of Blocking Victims . The bottom pane displays the Blocks by Chain table data by default, with another option to display a table of Blocks by Object.
The Details screen displays a table of all Blocking Details defined by the applied filters.