Symptom

When using the ‘Save to Excel’ option in Reporting Services, the resulting Excel file produces the following error when you try to open it:

“File Error: Data may have been lost”

This typically happens when the report is very complex and contains a lot of data or images.

Explanation

When a user clicks on the ‘Save to Excel’ button, the server generates an Excel file and sends this file to the user in a single HTTP packet. By default, the server will limit the size of this HTTP packet according to the maxRequestLength property in the web.config file (this is set to 4096KB by default). If the Excel file is very large, the end of the file becomes clipped, and data is lost.

Resolution

To resolve this issue, open the web.config file and set the httpRuntime.maxRequestLength property to a larger number (in the following example it's doubled to 8MB):

<configuration>
  <system.web>
    <httpRuntime maxRequestLength="8192"/>
  </system.web>
</configuration>

This sets the maximum HTTP packet size (in KB) and lets the server send larger, more complex files.

Note: If the <httpRuntime> element already exists in the web.config file, for example:

>httpRuntime executionTimeout="9000"/>

Then you will want to add the maxRequestLength attribute like this:

<httpRuntime executionTimeout="9000" maxRequestLength="8192"/>