Configuration of ChartPart
ChartPart for SharePoint depends on Microsoft .NET Framework 3.5 SP1 and the Microsoft .NET 3.5 Chart Controls.
By default ChartPart is configured to store the chart images created in the memory. To tune your SharePoint installation you might want to have it store the images on disk instead.
Use memory for temporary chart images
This is the default setting of ChartPart for SharePoint.
In the web.config appSettings you will have this element:
<add key="ChartImageHandler" value="storage=memory;timeout=20;" />
Store temporary images on disk
To store the temporary generated chart images on disk you have to open the web.config files and edit the ChartImageHandler appSetting like this:
<add key="ChartImageHandler" value="Storage=file;Timeout=20;Url=~/tempImages/;" />
Then you have to create the tempImages folder. The easiest way is to create a folder in the web application with tempImages as its name. You have to make sure that the users have write permissions on the folder.
Change the timeout settings for the temporary charts
You can change the timeout for all the temporary generated charts by editing the appSetting, described above. Just change the Timeout value to another value (in minutes).