AS 400 Performance from .Net iSeries Provider

Question

First off, I am not an AS 400 guy - at all. So please forgive me for asking any noobish questions here.

Basically, I am working on a .Net application that needs to access the AS400 for some real-time data. Although I have the system working, I am getting very different performance results between queries. Typically, when I make the 1st request against a SPROC on the AS400, I am seeing ~ 14 seconds to get the full data set. After that initial call, any subsequent calls usually only take ~ 1 second to return. This performance improvement remains for ~ 20 mins or so before it takes 14 seconds again.

The interesting part with this is that, if the stored procedure is executed directly on the iSeries Navigator, it always returns within milliseconds (no change in response time).

I wonder if it is a caching / execution plan issue but I can only apply my SQL SERVER logic to the AS400, which is not always a match.

Any suggestions on what I can do to recieve a more consistant response time or simply insight as to why the AS400 is acting in this manner when I was using the iSeries Data Provider for .Net? Is there a better access method that I should use?

Just in case, here's the code I am using to connect to the AS400

     Dim Conn As New IBM.Data.DB2.iSeries.iDB2Connection(ConnectionString)
  Dim Cmd As New IBM.Data.DB2.iSeries.iDB2Command("SPROC_NAME_HERE", Conn)
  Cmd.CommandType = CommandType.StoredProcedure

  Using Conn
   Conn.Open()

   Dim Reader = Cmd.ExecuteReader()
   Using Reader
    While Reader.Read()

               'Do Something

    End While
    Reader.Close()
   End Using

   Conn.Close()
  End Using

EDIT: after looking about a bit on this issue and using some of the comments below, I am beginning to wonder if I am experiencing this due to the gains from connection pooling? Thoughts?

Answer 1

I've found the Redbook Integrating DB2 Universal Database for iSeries with Microsoft ADO .NET useful for diagnosing issues like these.

Specifically look into the client and server side traces to help isolate the issue. And don't be afraid to call IBM software support. They can help you set up profiling to figure out the issue.