Lesson 6: Shifts

How They Work

By assigning a shift to a resource or activity, you create a fixed block of time when that resource or activity is available to work on entities. Shift files are created using a shift editor which can be called from the Shift tab of the Properties Dialog box for resources and activities. You can also create a default shift file by clicking the Simulation menu, selecting Options, then clicking the Files tab. Individual shift files assigned to a resource or activity will override a default shift file. Though you can assign a shift to either a resource or an activity or both, scheduling of activities is typically controlled by the shift of the resource working at that activity.

Once you assign a shift file in your model (or use Daily Pattern arrivals), you need to remember your simulation run length is now simulating a 24 hour clock. For example, a 40 hour run length no longer represents a week’s worth of working hours. 40 hours into a simulation now represents Tuesday at 4pm since all simulations start Monday morning at midnight.

By default, a resource on a shift file will work overtime if an entity is currently being worked on when the shift ends. If you want the resource to stop working and go off shift, you must check the option on the resource’s Shift tab to Interrupt current activity to go off shift or on break.

Let’s load our first model and begin working with shifts. Remember that the simulation run length is currently 40 hours. That represents five 8 hour days in straight work time. When we add shifts to the model we will need to adjust the simulation time to a 24 hour day.

Creating a Shift File

Open Lesson 1 – Call Center. Double click the Level 2 resource, then click the Shift tab. Open the shift editor by clicking the Create shift file button.

Shift File Editor

Create an 8 to 5 shift by clicking and dragging your mouse on the Mon line from 8am to 5pm. Don’t worry if you didn’t get it exactly right. Just click on the bar you drew, then adjust the starting and end times using the Begin Time and End Time adjustments at the top of the window.

Shift File Editor

Make sure the Monday shift is not selected by clicking the gray area around the time grid. Now define a lunch break from noon to 1pm. Click the Define Break icon Define Break Icon in the tool bar. Then click and drag your mouse from noon to 1pm on the Monday shift you just created.

Shift File Editor

Click the 9 to 5 button 9-5 Shift Icon next to the coffee cup icon to switch back to Define Shift mode. Click the Monday shift to select it. Click the Duplicate Day button Copy Icon Shift to copy the Monday shift. Hold down the Shift key on your keyboard and click anywhere in the Tue timeline to paste the Monday shift. Repeat for WedThu, and Fri.

Shift File Editor

Save your shift file as 8 to 5 and close the shift editor. Then click the Browse button and select the shift file.

Resource Shift Properties Dialog

Save your model as Lesson 6 – Shifts. Adjust the simulate run length to at least 120 hours (5pm on Friday). Assign a shift file to the Level 1 resource (either the same 8 to 5 shift or create a new one). Create a Daily Pattern arrival. Simulate your model.


1. Does your model have capacity to handle the calls they way have set them up?
2. Think of ways you could adjust your model to handle the load put on it.

Model Packaging

Now is a good time to discuss model packages since you have now specified a path to your shift files. As we have mentioned already, your model is made up of several files, now including your shift file. Moving your model to a new location, either on your hard drive or sending it to someone else is easy because of the package creation function.

Click File and select Save.

Saving a Model

Note the files listed. These are the files required to run your model. You could send your model by e-mail to another ProcessModel user. However, when they open the model, the shift file will be pointing to your hard drive location and they will get an error saying it can’t find the shift file.

By creating a package of your model and send the package file rather than the individual files, the other user would install the package rather than just opening the .igx file. By clicking File and selecting Install Package, the system will automatically remap the location of the shift file to the location selected by the package installer. This applies to simply moving your model to a new location on your own hard drive. When installing the package, a new shift file is copied and its location is remapped for you.

A model package is also a good way to backup your model for future retrieval. Just make sure you save the package with an appropriate name, uniquely identifying it. Helpful things to include in the name are the date, model builder, function of the model, etc.

Important! Be aware of one important issue when naming your files. With version 5.x and earlier, you cannot use periods in a model filename (e.g. My Model 1.5.3). You can use spaces, hyphens, or other delimiting characters, but not periods.


3. Model package are in a .zip format. Is it ok to use WinZip to extract model files rather than installing them from the File menu?

Continue to Lesson 7: A More Complex Call Center