Hi Ryan,

The excel and pivotable are designed for the personal scenario, not server
side, which means if you use them in the server side which will evolve
hidden error into your solution. This kb article will introduces the
limitation for you:
257757 INFO: Considerations for Server-Side Automation of Office
http://support.microsoft.com/?id=257757

Furthermore, pivottable, in fact, is the client control of OLAP service. So
if you are going to increase the performance, you should optimize your OLAP
server and make mostly all processing in the server side so that the client
side will spend little time on the calculation, which will give the user
one quick response UI.

Please feel free to let me know if you have any question.

Best Regards,
Wei-Dong Xu
Microsoft Product Support Services
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