Unable to process the request. Wait a few minutes and try performing this operation again.

Issue: Most of our clients were having issue while opening the Excel files from their SharePoint sites using Excel web access web part after an upgrade from MOSS 2007 to SharePoint 2010.

Error: Unable to process the request. Wait a few minutes and try performing this operation again

 

Troubleshooting done:

- Adding the URL in trusted file location.

- Change the settings to open the document with client application form document library. .

Resolution:

After some investigation we found this Blog from the technet , which talks about the same problem:

- Rebooting the server will remedy this, but that is not realistic.

- You can run IISReset /noforce that too should remedy the issue.

- To avoid a complete IISReset, you can manually recycle the Application Pool Running Excel Services. (Please check the blog for additional info)

http://blogs.technet.com/b/excel_services__powerpivot_for_sharepoint_support_blog/archive/2013/01/24/excel-services-2010-quot-unable-to-process-the-request-quot-maximum-private-bytes-size-exceeded-unable-to-complete-the-operation.aspx