To manage mirroring tasks:
The Manage Mirroring Tasks page appears and displays all active tasks and pending actions.

The resulting action depends on whether the subscriber is online when you stop the task.
Click CANCEL in that row to remove the mirroring task from the Manage Mirroring Tasks page.
Click Details in the Pending Due To column to determine why the action is pending. To force the cleanup of any task in the pending stop state, use the Force Cleanup button in the Pending Actions table, which you get to by clicking the Details link.
Use the Force Cleanup button only when the traffic-mirroring service activation has been removed or the subscriber has been removed from the system and will never log in again.