Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. The statement has been terminated

When you facing this issue its means the timeout is expire.In your code where you run the stored procedure you should have something like this:

SqlCommand c = new SqlCommand(...)

//...

Add such a line of code:

c.CommandTimeout = 0;

This will wait as much time as needed for the operation to complete.

Ref:

http://stackoverflow.com/questions/8602395/timeout-expired-the-timeout-period-elapsed-prior-to-completion-of-the-operation