If you are manually choosing your connection, you have the option to Load Summary Resource Assignments when you launch Project Professional. If you are not manually controlling your connection, you may have no idea what I’m talking about. 
Before I explain the Summary Assignments, I’ll first walk you through how to see the option when you connect to Project Server.
1. In Microsoft Project Professional 2010, choose File –> Manage Accounts –> Configure Accounts.
2. At the bottom of this dialog box, select Choose an account and then click OK.
3. Exit Project Professional.
4. Launch Project Professional and you will see the following dialog box, allowing you to select the option to Load Summary Resource Assignments:
Now that you know how to find the option, let’s talk about what it means. It’s quite simple, actually. Checking the option will allow you to see how a resource is assigned across all Enterprise projects even though you only have one of those projects open. It won’t let you see all of the task details, but will show a summary of how a resource is assigned in other projects.
For example, if I don’t check the option, when I go to the Resource Usage view I will see ONLY the assignments for resources within the project that I have open:
However, if I Load Summary Resource Assignments and apply the Resource Usage view, I’ll see a summary of other project assignments:
Loading those summary assignments just makes a resource’s total workload visible within any given project.
Happy Scheduling! 
