.NET web 2.0 API, 503 Service unavailable

I created a .NET web 2.0 REST GET API. which reads reads a large XML file and then insert the data in Database (SQL Server). But when I run the API, then, after some time browser/Rest-Client returns 503 service unavailable message. Works fine when I run the API on localhost, but gives the above error when I publish my app and connect to Live Server.