Web API alternatives to save a file to server's file system

We have a SQL Server 2012 Enterprise edition and an ASP.NET Web API 2.2 web service. The web API is the public interface for the database.

We need to end a production order doing:

1. Changing a value in Production orders table.
2. Generate a XML with all data related to this Production order.
3. Save that XML file into server’s file system.

I have thought to do it with a POST to Web API, but I don’t know if I have to do the three previous steps ( Changing value, generating XML and saving it) in a Stored Procedure or maybe in the Web API Controller.

Maybe, if I do it with the API controller, it will take a long time and the client will time out.