Resources constrain when work can take place at Activities. For instance, a machine can only work when there is an operator available, and a doctors’ appointment can only occur when there is a doctor present
To add Resources click on the Create Resource button on the left toolbar, and then click on the screen. The Resource icon will appear:
The next step is to assign your Resource to an Activity. Clicking on the Activity opens its properties on the toolbar, and you can choose the ‘Resource’ option from here. Click on Add and select the appropriate resource from the list. Click OK and your resource will then be assigned to that Activity. Assign your resource to all three Activities within your simulation.
The number above the Resource indicates the number of resources available; the default is 10. Click on your resource to see its properties on the toolbar. Change the number of Resources available to 3, and run the simulation. You will see the number above the Resource change between 0-3 depending on the number of Resources in use at any one time.
Try reducing the number of resources available to 2, and re-run your model. The resource will now be working as a constraint, and restricting the number of items which can be processed at a time.