Cameo Simulation Toolkit creates a simulation session(s) while a model is being simulated. A simulation session contains a context with a specified runtime value. The context of the simulation session is the executing UML element that can be either a Class element or a sub-type of a Class. When the context element is simulated, a runtime object will be created to store the simulated values. 

You can create multiple simulation sessions during a single simulation, such as an Activity simulation. If the simulated Activity contains any callBehaviorAction, a new simulation session will be created to simulate each callBehaviorAction. The Sessions pane will display all simulation sessions during simulation and order them by context elements in a tree node, as shown below.

The Simulation Sessions pane.

You can open the Simulation clock dialog to see the simulation clock in real time by right-clicking any context elements in the Simulation Sessions pane and selecting Show Simulation Clock.