By default, ASP.NET limits the size of files that can be uploaded to a server to 4 MB. If your model is more than 4 MB in size and you are unable to deploy it to a server, change the default value in the web.config file for each report server to which you want to deploy the model. To change the default value, open the the web.config.comments file in a text editor, copy the maxRequestLength element from the <httpRunTime> section of the file, and paste it into the <httpRunTime> section of the web.config file that is located in the report server installation folder. After you paste the element into the file, change the default size to the size that you want to use.
Typically, the web.config.comments file is located in the following path: <drive>:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG.
Typically, the web.config file for the report server is located in the following path: <drive>:\Program Files\Microsoft SQL Server\<instance id>\Reporting Services\ReportServer.
If you want to upload large models using Report Manager you must repeat the steps outlined above for the Report Manager web.config file. Typically, the web.config file for the Report Manager is located in the following path: <drive>:\Program Files\Microsoft SQL Server\<instance id>\Reporting Services\ReportManager.
If you want to change the settings for the entire server, repeat the steps outlined above for the machine.config file. Typically the machine.config file is located in the following path: <drive>:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG.