I have the following insert which executes in < 1 sec in the VB Demo tool but takes 4 - 5 from the .NET code. I open the connection once and perform all the operations (inserting several sales orders) on the same connection.

insert into SalesReceiptLine (RefNumber, TxnDate, DueDate, CustomerRefFullName, ClassRefFullName,
 Memo,  PaymentMethodRefFullName, CustomerSalesTaxCodeRefFullName, ItemSalesTaxRefFullName,  SalesReceiptLineItemRefFullName, SalesReceiptLineDesc, SalesreceiptLineQuantity, SalesreceiptLineRate,   SalesreceiptLineClassRefFullName, SalesreceiptLineAmount, SalesreceiptLineSalesTaxCodeRefFullname)
Values ( 'SO100004',{ d'2007-09-05'},{d '2007-09-05'},'OTC Consultant','TX','CustName',NULL
,'Tax', 'BlueNet Sales Tax', '4200','Port Authority - White w/  Visor',3,14.99,'TX',44.97,'Tax')

My selects and even deletes (i use Jump-Ins in the where clause) happen very fast. I am puzzled as to why the inserts should take so long. I don't know how to analyse the performance further. Is there some place (like SQL trace) where I can look to see which sub operation is taking long?

Try looking at: ASP.NET vs Classic ASP 

Thank you. The post refers to ASP.NET and I am trying this from a C# .NET Windows Console application. I am guessing the VB Demo app was written in VB 6.0. So, I tried the same insert using VB6 using ADO library and the insert ran quite fast (<1 sec). Are you aware of some settings in .NET ODBC connection or command that is causing the delay? When I turn on the QODBC trace, the insert statement is causing "Open table" operation on Sales ReceiptLine table which is taking upto 6 seconds and longer sometimes (basically all the delay is from this Open table operation) . The same operation shows up even from VB6 but completes immediately. Here is the code in C# .NET that I am using. Thanks!

OdbcConnection conn = new OdbcConnection(QBConnectString);

conn.ConnectionTimeout = 300;

conn.Open();

OdbcCommand command = new OdbcCommand("insert into ......");

command.CommandTimeout = 300;

command.Connection = conn;

command.ExecuteNonQuery();

See the msdn .NET Framework Developer Center:  http://msdn2.microsoft.com/en-us/library/system.stathreadattribute.aspx

Note: ADODB works, but when you loop through the resultant recordset via Recordset.MoveNext(), an additional query is made through QODBC for each record.  These additional queries caused an additional 50 minutes of runtime for a 7000 invoice query.

The first function below demonstrates the ADODB method that took ~1 hour.  The second does the same thing with ODBC and takes less than a minute. 

[STAThread]
static void test1() {
    ADODB.Connection con = new ADODB.Connection();
    con.Open("DSN=SOQB;OLE DB Services=-2", "", "", -1);
    string invoiceSQL =
                "SELECT CustomerRefFullName, RefNumber, TxnDate, BalanceRemaining, AppliedAmount, Memo " +
                "FROM Invoice " +
                "WHERE TxnDate>{d'2006-04-02'}";
        ADODB.Recordset invoiceResult = new ADODB.Recordset();
        invoiceResult.Open(invoiceSQL, con, ADODB.CursorTypeEnum.adOpenStatic, ADODB.LockTypeEnum.adLockOptimistic, 0);
        while(!invoiceResult.EOF) {
                Console.WriteLine("Invoice #" + invoiceResult.Fields["RefNumber"].Value.ToString());
                invoiceResult.MoveNext();
        }
        con.Close();
}


[STAThread]
static void test2() {
        OdbcConnection con = new OdbcConnection("DSN=SOQB");
        con.Open();
        OdbcDataAdapter dAdapter = new OdbcDataAdapter(
                "SELECT CustomerRefFullName, RefNumber, TxnDate, BalanceRemaining, AppliedAmount, Memo " +
                "FROM Invoice " +
                "WHERE TxnDate>{d'2006-04-02'}", con);
        DataTable result = new DataTable();
        dAdapter.Fill(result);
        DataTableReader reader = new DataTableReader(result);
        while(reader.Read()){
                Console.WriteLine("Invoice #: " + reader.GetString(1));
        }
        con.Close();
}