Latency between SQL Server 2005 and .NET

Question

This question is an follow-up of an previous asked question.

I've written an simple program who looks like this.

string s;
do
{
  using (SqlConnection conn = new SqlConnection("POOLEDCONN"))
  {
    using (SqlCommand cmd = new SqlCommand("", conn))
    {
        s = (string) cmd.ExecuteScalar();
        Code2IncrementPerfomanceCounter
    }
  }    
} while (!string.IsNullOrEmpty(s))

The query returns an string(nvarchar(max), current maximum size 9k), there is a lot of latency between SQL Server and .NET. The SQL Profiler says that the query has an duration of 0 ms, so I think it isn't the database. The network is responding in less than 1 ms so it shouldn't be the network.

If I run this code on our testserver(VMWare, SQL isn't virtualized) there will be a max of 600 loops per second. The application doesn't consume more than 5 % cpu. Why isn't it going faster? Must I use streaming to get the data from SQL or something else?

Thanx in advance

Answer 1

600 calls per second is one call per 1.7 ms. If your latency is 1 ms, and Sql Server adds a little to that, that seems like a plausible result?

Answer 2

I have three different things you need to look at:

1. Is your web server connecting to the DB Server with the TCP/IP or are you using a different protocol?
2. How busy is the network on the machine running the dtoNet process?
3. Does the performance go above 600 processes/second if you remove the SQL call and leave only the performance counter logging?

Answer 3

Opening and closing the SQL connection is expensive. Can you just do that once instead?