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    <p>I use OracleCommand.Fetchsize to improve perfomance on large Queries.</p> <pre><code>cmd.FetchSize = &amp;H100000 '1Mb Dim Rdr = cmd.ExecuteReader </code></pre> <p>Some time ago, I use Async Readers for get Blob Data. But to use Async Reader you need maintain an array with each async Result an loop until last Reader ends.</p> <pre><code> Public Shared Function FromBlob(ByVal Id As String, ByVal Rv As String, ByVal cn As OracleConnection) As Proyecto Dim n As Integer, Prj As Proyecto = Nothing Dim Bf(2)() As Byte, arrAr(2) As IAsyncResult 'Para proceso asíncrono Dim Cmd As New OracleCommand( _ "Select rv,fecha,Datos From Proyectos Where Id=:Id and Rv in (:Rv,'Av','Est')", cn) Cmd.BindByName = True Cmd.Parameters.Add("Id", OracleDbType.Varchar2, Id, ParameterDirection.Input) Cmd.Parameters.Add("Rv", OracleDbType.Varchar2, Rv, ParameterDirection.Input) If Rv Is Nothing Then Prj = Proyecto.Actprj Try Using Rdr As OracleDataReader = Cmd.ExecuteReader Do Until Rdr.Read = False Dim rv1 As String = Rdr.GetString(0) Select Case rv1 Case "Av" : n = 1 'Avance TND Case "Est" : n = 2 'Datos Seguimiento Estudio Seguridad Case Else : n = 0 End Select If Rdr.IsDBNull(2) = False Then Dim Blob As OracleBlob = Rdr.GetOracleBlob(2) Dim Buffer(CInt(Blob.Length)) As Byte Bf(n) = Buffer arrAr(n) = Blob.BeginRead(Buffer, 0, Buffer.Length, Nothing, Blob) End If Loop If Bf(0) Is Nothing AndAlso Prj Is Nothing Then _ MessageBox.Show("Fallo al cargar proyecto") : Return Nothing For n = 0 To Bf.Length - 1 Dim ar As IAsyncResult = arrAr(n) If ar IsNot Nothing AndAlso ar.AsyncWaitHandle.WaitOne() Then Dim blob As OracleBlob = DirectCast(ar.AsyncState, OracleBlob) blob.EndRead(ar) blob.Dispose() If ar.IsCompleted Then Using rd As New BinReader(New MemoryStream(Bf(n))) If n = 0 Then Prj = New Proyecto(rd, False) Else Dim entry = Proyecto.Entry.FromLob(rd), Index = Prj.IndexOf(entry) If Index &lt; 0 Then Prj.Add(entry) Else Prj(Index) = entry End If End Using End If End If Next End Using Catch ex As Exception MessageBox.Show(ex.Message) End Try Return Prj End Function </code></pre>
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    1. POHow to improve performance by processing database results in parallel?
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    1. CONote: When I use BeginRead (Async), I do´nt use multiTask on my app, Oracle executes simultaneus readers over assigned buffers (Bf). I only need verify each IAsyncResult for task completion. In code sample for three readers the result is about 50% fast, but this is for reduce roundtrip, not for Data Size.
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