Have you ever wondered which entity attributes can be set when creating or updating a record? There are a few places you can find this information:
The Metadata Browser
This is a live view of the metadata for your organization. It can be found here: http://<yourservername>/sdk/list.aspx
If your server is not installed on the default port, the URL includes the port. For example, http://adventureworks:5555/sdk/list.aspx
Next, click the icon in the definition column to see a list of all the attributes for the selected entity. Look at the last three columns in the first table to discover whether the entity is valid for create, retrieve and update operations.
The SDK
The SDK contains similar information for each attribute. Look at the entity reference pages in the SDK: http://msdn2.microsoft.com/en-us/library/aa683648.aspx
For example, if you look at the reference page for the campaign.istemplate attribute: http://msdn2.microsoft.com/en-us/library/aa680744.aspx
You can see from the table that this attribute is valid for create and retrieve but not for update.
What happens if you set an attribute valid on create or update that is not allowed? The system will ignore any attribute values that are not allowed for create or update.